Hello! Thank you for starting this topic of discussion. I was considering reaching out to you to discuss exactly these issues. As such, I already have some things to say. Apologies for the "wall of text" that follows.
SEED USAGE VS "TRUE" RNG
For those that wish to have longer/less predictable runs, it would seem that requiring a "random" seed is a good solution. But this solution presents 2 problems. The first is that even with a "random" seed, the ideal run would still look similar to what I've already done by design in my current WR (I did find the seed by accident in the first place). Someone interested in grinding such a category would just keep "resetting" until they got a wormhole close by, send scouts through that wormhole while building their fleet, and hopefully find the other race near the other side. It would be longer... but I bet a sub 5 minute time wouldn't be too hard to get. Would that really be a better speed run? The other issue with that kind of rule is... how do you enforce it? I'm mean, sure... you can't type in a seed manually, but what's stopping someone from resetting as soon as they've seen the seed and waiting until they see one they're familiar with. A clever player working within those limits could pretend that they don't know what to expect, but still have a competitive advantage over someone who is working with a mystery seed. I just don't see what value would be added to the leaderboard by having categories with that restriction. The rest of what I have to say assumes that seed setting remains allowed.
CATEGORIES BASED ON GALAXY TYPE
This could potentially be interesting. With either Cluster or Spiral types, the game is forced to continue until you can travel through unstable wormholes. You would be forced to colonize within your area a little and attack the other race's sector before they can leave their own. Even if an ideal seed is possible, finding it would be a lot harder. You'd want one that gave you good systems in your area, and hope they have bad systems in theirs. And figuring out a good custom race would be interesting (less easy penalties). The game might last long enough that I imagine there would be some variety in the AI's behavior. The focus would be on speedy micro-management in the early game, and speedy conquest in the late game.
CATEGORIES BASED ON GALAXY SIZE
This doesn't change much by itself, honestly. With wormholes in the right locations, the size of the galaxy is irrelevant.
CATEGORIES BASED ON STARTING AGE
Pre-Warp would just force some research at the front end. A custom Lithovore race can focus on science early and switch to full blown production when necessary while the other race it forced to balance with farming. You might be able to get to the enemy before they colonize a second planet. Advanced would give the enemy some extra planets to conquer. Would take some more work, would be harder to optimize, but with a good seed it's a solvable run.
CATEGORIES BASED ON DIFFICULTY
Not sure what this would change honestly. I think the higher difficulties mostly gives the enemy more starting money. They'd probably buy more ships to defend themself before you got there. Not a major difference in how the game is run I would imagine.
CATEGORIES BASED ON NUMBER OF OPPONENTS
This changes how the galaxy gets seeded. Each amount of opponents would have a different optimal seed. And at higher numbers, the RNG might become unpredictable by the time you get to the last races. Also higher numbers require bigger galaxies (1-4 is small, 5-6 is medium, 7-8 is large).
CATEGORIES BASED ON GAME PACE
Regardless of whether we use a prefabricated paces or customize the "speeds", this wouldn't change much. In my WR I used very slow research so that the enemy wouldn't develop better defenses, very slow population so they would have less things to bomb, and very fast production so I could build my fleet in fewer turns. If I were forced to have the opposite setting, it would take a little longer... but would probably be just about the same run.
CATEGORIES BASED ON MISC. ADVANCED SETTING
I mean... what would be the point? pirate%? I'm not even going to entertain these.
CATEGORIES BASED ON VICTORY CONDITIONS
These are the logical categories to go with, but it would still be a matter of finding/grinding seeds. I actually already toyed around with this (didn't record any of it yet though). Diplomatic victory requires two other races, I had to find a new seed, but pretty quickly I found a pretty good one. I built as big a fleet as my one star base would allow, split it up to the two homeworlds, bombed them down to 1 population each, then voted myself ruler of the galaxy. Took less than 5 minutes. For Technology, I did that same as my Conquest victory, but didn't finish the enemy and did colonize a second planet. Thanks to auto-turn, I didn't see the point of exploring for more planets to colonize, just sail though the tech tree. Was less than 15 minutes, I think. Economic victory was like a mix of Diplomatic and Technology. Two enemy races(I used same seed as I did for Tech), bomb them down to one pop, grind research until you get the stock exchange, build it, buy stock, wait 10 turns. Took less than 10 minutes. Antaran Victory is a tricky one. I did the one race seed, bombed them down, but I needed a big fleet so I needed colonies for star bases. It ending up feeling like a real long play of the game(might have been a few hours, but I didn't play optimally). I don't think I'd want to compete for that category AND watching/approving the submissions would be a pain in the butt. Same would be true, I imagine, for an Orion%.
Is there anything else that can be restricted to make the game different? Would it make sense to restrict the use of custom or DLC races? Wouldn't change much honestly... my original submission used the Bulrathi. Requiring random opponents would just mean more resetting.
A good way of doing things might be to pick just two ways of splitting up the categories, using one as main categories and one as sub-categories. For example, Galaxy Type as main, and Victory Condition as subs. With Galaxy type we could mix in some other requirement, since Spiral and Cluster are pretty similar to begin with. Maybe Spiral has a minimum of 3 races (one per quadrant, neutral quadrant in the middle, I think is how that would normally shake out), and maybe cluster has a minimum 7 (one per cluster). Diplomatic Victory would be a pain in the butt in a cluster galaxy because all races have to meet all other races. I would probably invade all but two neighboring empires and wait for them to meet so I can out vote them.
We could make categories with a collection of setting restriction to fit certain themes, like Pacifist. This would make the quick strategy I used fir Diplomacy not work. It might become advantageous to turn on 'minor civilizations' and purposely seeking out those systems to add their population to our votes.
I honestly don't know what the best course of action would be. And lets be real... only two people "follow" this game right now... you and me @KrayzarKrayzar. If we think more people will come along, what would be best for them. Too many categories and convoluted rules might scare some people away. But if we just do some straight forward categories(just Victory conditions for example), then pretty quickly we'll post up some runs with good seeds/strats and new players might feel forced to play established routes, which isn't always fun. It's quite the dilemma.