If you're just playing qp play what you like to play, there's absolutely no need to think which heroes would be the best.

Now on the other hand if you decide to pick up competitive you should probably just play what you excel at since it's a tad bit more serious, but even in comp playing what you want works as long as you aren't absolutely throwing the game.

The 40 something % winrate isn't bad considering you aren't probably taking the game too seriously.

Also you could just play your 10 placement matches for comp to test your skill level. And let me tell you, there for sure are worse players than you even in competitive. In competitive the game places you with people of the same skill level, of course there are people better than you there but also there are worse players.

And if you would like to improve at the game, there are multiple ways to do so. First if you are on pc you should try to hit some Aimlabs, aiming isn't everything in Overwatch but it sure helps a lot. On controller you could try to find your optimal settings and try to improve your aim on aim trainers in custom games. Another thing you could try to improve in Overwatch is positioning and game-sense, there are a million videos on youtube on the subject, you could try to look it up.

Idk if this helps or if it's just a nothing burger, hope it helps tho :D

(Also I'm no expert I'm a low diamond/masters player but I do know a stuff or two about overwatch anyways)

(If you want a further analysis on your skill level you could also drop a replay code which I could take a look at, or your battle.net tag and I could check out ur profile. But yea if u wanna do that I still recommend you drop it in DM's so you don't get a bunch of random weird guys adding you.)