Which 5* to raise for PVE 10?

Marvel Puzzle Quest MPQ Tips and Guides
1

Hello,
I just reached level 120 yesterday and I wonder which 5* I should raise now for PVE SCL 10. I mainly use Okoye (541, the powers, not her level) + iHulk 110 (+ Polaris 454 when a third is allowed). I also regularly fight with Kitty 331 + Polaris 454 (+ Grocket 355). I also use other characters such as Medusa, Jug4, or Vulture depending on the context.
I have 500 shards for Okoye. I thing the short-term best option would be to raise her to 551 to increase her longevity in battles but that would diminish the likelihood to pull a useful cover later (1 chance out of 3 instead of 2 chances out of three if I instead raise her at 542). So I have a slight preference for 542. What should I do with the 500 Okoye shards?
I have just earned the black Okoye cover from Shuri who was receiving the 4* shards. Shuri is now 20 covers away from the next 500 Okoye shards. Since Shuri does not have a 3* feeder, I think that using her that way is not efficient. I think that I better wait for an Okoye special vault or 250-CP covers for the last to ones and forget about raising her with 4* and 5* shards. Should I keep raising Okoye with (Okoye + Shuri) shards or focus on other characters?

I heard that BRB is a very strong asset in PVE 10 with Polaris. Slow but safer than most offensive options. I only have a blue BRB cover. Throg is championed at level 271 => 9 covers away from a green BRB cover but no 3* feeders for Throg.
So one possibility could be keeping shards on Cyc3 → Emma → Kitty because I do not see other good 3* shard options, and focus on Throg and BRB for the other shards. So should I focus on finishing Okoye as fast as I can with shards though that would be very slow (20 Shuri covers away for 500 Okoye shards and no 3* feeder), or focus on Kitty for Polakit (+ Grocket) (a rather fast option because there is a 3* feeder and because I am only 6 Emma covers from 500 Kitty shards), or focus on BRB which will take time (only one blue cover right now, 9 Throg covers away from a green BRB cover and no 3* feeders), or focus on another character? I do not see a big advantage in raising iHulk beyond 110 over other 5* options.
I thank you for any piece of advice.

2

It will be very interesting what 5* players think about this.

Kitty and BRB have the best synergy with Polaris. You only need one BRB yellow (preferably 3) to get the winfinite with 1* Juggernaut or 4* Thanos and you are so far away from champ it seems unnecessary to focus on him for now. Kitty is the real wildcard. She has great synergy with Polaris and Grocket. But Hammer Juggernaut has pretty good synergy as well so missing out on an optimized Kitty/Polaris combo seems like it would not hurt too much.
Okoye is, of course, amazing and has synergy with numerous 4* characters, far more than Kitty, and even with Polaris. Running her with Silk and 2099 is also great. And you already have iHulk so pretty much would be able to handle most nodes in SCL10, though might have trouble with the hardest ones without a broader 5* lineup. Since you are so close with Okoye I would personally just concentrate on finishing her off first. I would also be tempted to switch to 1/2 Thor after and trivialize PvE altogether.
My opinion is not based in experience so take it for what it is worth