This entire post (excluding this introductory sentence) is my own opinion. Plz no trigger
Defenders best to worst: Valk, Caveira (Casual only), Echo then frost/Caveira in ranked.
Attackers best to worst: Hibana, Capitao, Buck, Blackbeard.
IMO, of course.
Caveira is a hard roamer, and playing her any other way is pretty wasteful. Either Shotgun or SMG. Both are good. Impacts are probably best to help you snake about. Complete pub stomper.
Pretty sure I've already covered Valk.
Barely see Frost, but you have to be unpredictable with your mats. The SMG is good if you can land headshots. Otherwise take the shotgun and hold down a close angle.
Echo is a camper, but the middle of the objective isn't always ideal. Especially now since Fuze is so popular. Shotgun is laughable and SMG is a headshots machine. Use Yokai as another camera, the mobile eyes of your roamers or to slow a push onto site. DO NOT SPAM STUNS. They have long cool down and last 8 seconds if they target doesn't move, 13 if the target walks and 17 if the target runs, so there is no need to spam them as they don't stack.
Hibana is your hatch or head glitch opener. One shot opens a hatch and if you shoot 4 of the clusters you've given a teammate a great headglitch. Don't know anyone who doesn't use Type + bearing. Your mobility and reliable gun allows for hard, aggressive pushes once you've done your job.
Capitao is active area denial. His gadgets are most useful when securing the objective as they completely negate access to a certain area for a few seconds. Doesn't sound like much but when you're securing the area or you've planted the bomb? Those few seconds are huge. So he's most useful towards the end of the round. For this reason it's best not to rush in and try to stay alive, because you have the potential to concrete a win if your team can get into the obj.
BB is pretty simple. Head glitch and profit. He's... Less useful but not completely useless. Your shield will still save your life but you need to look after it. Don't make obnoxiously slow peeks because they'll pummel your shield before your head is around the corner.
Buck is extremely versatile but he is extremely versatile. His gadget is useful but not game changing. This is great because you can open up holes from the floor above (to shoot cock-block gadgets or get los on the enemy) and if you die, it's not end of the world for your team. The underbarrel shotgun also doubles as a secondary with a miniscule swap time. This means you can very quickly take out an enemy long range and then peek around a close corner with the shotgun for a second kill.
For all the Attackers the AR + throwable gadget is probably better.
For Echo, your only real choice is the SMG. Valk and Caveiras weapons are all great. For Frost, get headshots or use the shotgun.