First let me be clear about speedrunning this game, do not come thinking that you can take a world record just because the game isn't being run by a lot of people, if you truly want to be competitive, there's a few basic steps that you would need to take as a competitor to really begin to shape yourself as competent runner.

How do I pick my characters for a run?

For the regular cast, there's a few factors to consider.

1.- A character that can deal a lot of damage with very few hits, that also happens to have a reset tool in his kit if possible.

2.- A character that can easily deal with the gigants and can be use to quickly deal damage.

3.- Some degree of synergy between said characters.

Now that we know the basic premise, there's a few options in the cast that can potentionally be used to get a better run, for potential damage characters, we can go into the following ones:

Soki

A strong character with a kit that allows him to go into resets fairly easily when getting the hit, his long range pokes and big buttons allows you to quickly go into small but powerful sequences that can yield heavy damage and even go as far controlling the midrange game. His main weakness as the damage dealer is that his supers are terrible to use against the gigants and you rather not use them at all in any run unless you double super.

Tekkaman

As strong as soki in terms of damage, and able to quickly deal damage by simply going into jumping H repeatedly, his damage and supers are strong, and he can deal rather efficiently with the gigant at stage 4, but is not as good against the final boss, but he's capable of filling in both roles as a character.

Alex

There's 2 main reason you may want to use him, his superman dive which is jumping H, and his ability to reset the opponent with his specials, he's also able to snapback a character, allowing you to finish up an opponent should they tag out without dealing the killing blow, he's able to reset his grab in the air, so is an inmediate source of damage when you needed, his lvl 3 can deal with the lightan and ptx but not with the final boss, so he is not as good when using meter, but he can do an advance technique known as superman dive loops, which is doing Jumping H, into an air tag, but whiffing the air tag hit so that alex can continuesly dive into the opponent, it is a strong inmediate source of damage if you can master it against the final boss, since it can quickly deplete it's health bar.

Tekkaman blade

Probably the best damage dealer in the game when it comes to speedrunning, is not that he does the most damage, but he can quickly reset the damage counter and has the inmediate faster combos, he also has the best touch of death when using meter to gain red life and it's also the fastest tod, while he has the biggest ceiling in terms of skill, the reward for using him is ultimately the best result for a speedrun.

Now let's cover the gigant killers, the characters in this category are use to deal with the gigants as fast as possible, this includes lightan, ptx and the final boss, the characters to look out for are the following:

Zero

While zero himself doesn't deal that much damage unless you actually go for his advance combos, he can deal with the gigants using his buster charge shot, sougenmu super and rekkoha are great supers that deal with the gigants pretty consistently, so if you want, you can use zero for this role.

Doronjo

This character primary strategy against the gigants is to use her rock special in the air to deal damage, she's also capable of going in with jumping H, calling the rock, jumping H again and then try to get to repeat the process, her gigant rock super also deals a considerable amount of damage to the gigants, so it's always a choice when having the sources to deal with them.

Saki

She's probably the best gigant check in the speedrun category, because she has inmediate damage to the gigants with her jumping H into grenade, which she can then jump for another jumping H into grenade, and because the hits doesn't always combo it deals quite a lot of damage, her supers while not the best are still usable in dhc situations to close out a game, as well as double supers, as a bonus, her assist is capable of causing unblockables, but the cpu doesn't think that much, but is still a nice option to have.

Megaman Volnutt

His main damage comes from using weapon change to quickly fire his jumping H bullet, follow either by his special gattling gun or his super, both of which deals a good chunk of damage, he's also capable of holding his buster to deal a bigger shot, so that's something useful, you can combine this big buster shot when doing his super, so the moment the super ends, he can go into his buster shot for more damage.

.::Now let's cover the gigants::.

Realisticly lightan is the best speedrunning character, he boost the highest damage to reset damage, can deal the fastest touch of death and has the best reset situations, his only problem is the final boss, which can go either way on the highest difficulty because it has a grab, so it tends to be a problem, but you can circumvent this by using his 4b baroque into 4b to quickly dispatch the final boss, ptx is not that good in speedrunning so i don't recommend using him at all.

Other things to consider when speedrunning, if you really want a world record, practice a combo that kills the opponent when you have more than 20% red life, this can save so much time during a run that not using a tod is basically neglecting time save, learn your confirms, adjust for drop combos, be sure that everything you do can be corrected into a reset situation if needed, don't sit on meter, if you have meter, either use it for megacrash to gain red life so you can kill faster, or use it on quick supers to deal damage.