Games > All games > platoform filter to PS4 should tell you which games you can run.

Most communities do not require an embed timer on your video. What you can do is use a physical timer for yourself during the run, then later use timestamps on the video recording to get a precise time for submission. Even if you make a mistake, game mods will likely catch it and fix it.

Well let's break this down and see if we can't get these questions answered, eh?

1.) As far as what games to try out, honestly you can speedrun just about anything. Some genres don't really lend themselves to speed (visual novels, guitar hero, ect) but to be fair that doesn't stop people from trying. You mentioned Celeste. Celeste is an amazing speed game without a doubt, but i personally recommend starting with a game you have beaten before. It's a lot easier to understand the game and how the run works when you have played through the game already.

2.) For timing, as long as you have an accurate timer it will be fine. Even if you have to re-time the run after you finished, it should still be fine. Most communities don't require the timer to be on screen so I wouldn't worry too much about that. A lot of us do have a timer on screen because we stream our attempts and it's good for the viewers. Using a timer on your phone or something would be fine for you to see how your pace is or what your final time is.

I hope that answered your questions. I'm sure some others will have more insight as well.

I only have a PS4. I have set it up to stream via Twitch for easy recording (simple enough to do within the PS4).

I speedrun Streets Of Rage 4 as it uses in-game time so I don't need to re-time it afterwards.

You can build up your stream using a PS4 mic, camera or there is a way to stream your PS4 via a PC. However just streaming from the PS4 itself will suffice.