Everything
I'm trying to find gameplay but idk.
Neutral, mixups and general gameplay tbh
Here's what you need gameplay wise: Watch Sesal Snow, Atai, me, Pfidude, there's several others in the match video thread as well.
The core of your neutral/footsie game is gonna be forward 2, sweep, back 1 and shield bash are some of the core ways he plays neutral.
My play style puts shield bash at the forefront. I play him very chip/pressure heavy but also lots of zoning depending on the match up. Trait is super good in most match ups to give you the footsie advantage especially against characters you aren't reliably zoning.
Shield bash is so important to my play style because it gives me a safe 50/50 with sweep and Back 2, shield bash. It gives him a safe advancing special AND a safe advancing footsie normal with forward 2 into shield bash.
Jump 3 and jump 2 can be used for some ambiguous jump ins, I use jump 3 a lot for meterless block pressure since it's plus enough to beat out fast reversals with throw, down 1 or block string/stagger into throw or pressure. Jump 3 on block into shield bash is a true blockstring as well.
The beauty of float is how many applications it has for offense and defense. You can use it to make wake ups, pokes and many attacks whiff and punish on the way down for full combos as well as setting up ambiguous cross ups. It can also be used for baiting like for example, I played a Grodd player yesterday and did float, projectile to punish his anti-air or float backwards into jump 2 to make his charge whiff and punish it. A lot of his depth comes from flight.
When it comes to his ground mix ups, I think something that needs to be emphasized is that he isn't a super mix heavy character. He has some solid mix, but you don't wanna over extend on it since several are unsafe.
Back 2,3 should be apart of your ground mix up game, even if you don't do it often because it's overhead, overhead that crosses up meaning that Blue Beetle can mix that up with Back 2, low stab. The MB low stab leads to full combos but both options are unsafe. Back 2, MB bounce cancel forward 3 is good if you've conditioned well with back 2, low stab but you're gonna wanna use that sparingly because people can see it if you do it too much.
Beetle builds a lot of meter because the core of his gameplan revolves around abusing safe specials like energy cannon, float, shield bash etc so he always has meter. Don't buy into the no damage hype either. He gets over 300 around 360 ish for a one bar combo punish for example. He doesn't have the best damage, but his damage is very serviceable.
When you watch all the different Beetles, you'll quickly pick up on the reality that his design allows for a lot of creative freedom in how you approach playing as him. You've got crazy set ups and shenanigans with Sesal whereas with me you have more of a basic zoning, footsies and safe based style. There's no set be all end all play style, he has tools for pretty much every situation so you have the comfort and freedom to create your own way to play.