I think we still need to aim for a 1st team LB, and if Amass is good enough, he can challenge Shaw for 2nd LB, or even rotational LB.
Shaw' was solid but not spectacular last season, is getting on so will probably play worse next season, and is injury-prone. We'll let him go at the end of his contract (at least we definitely should), so we know we need to replace him eventually. If Amass does develop well and is ready for minutes, he can be cup/sub LB next season, and if he's truly great he'll challenge for 1st after a season or two. It also means that if it doesn't work out, we won't need to buy 2 LBs in 1 transfer window.
For me, that's the best case scenario, as that would allow us to maybe even let Shaw go early for a cheeky 5-10 mil. The whole team/squad needs to continually evolve, and he's hardly the type of legend that we owe him that much loyalty (and I think we've already shown a lot).
For the RB position, it's got to be next summer (at least winter). I think Maz can play better than Dalot, but Maz often needs a run of games to do so, and he's been so injury-prone. Dalot can be very frustrating, but like others have noted, he's got a great engine and he doesn't leak that many goals now. And having a good/great LB who often overlaps may even mean we don't need him to do as much on the ball - instead of actually getting the ball, he can hopefully just help stretch the play with his runs. Ultimately we'll need to make a decision as to who to keep, and I think giving Maz 1 (or even just half a) season and they can fight it out, and we buy a great 1st team RB next season to relegate them to a 2nd RB.