What happens for next season really depends on who sticks around and how they are prepared to contribute for next year. I do think that with the current players tabbed to play for BYU next season, we might need less from the portal than we think. But, there's a LOT that can happen - it's hard to trust what the roster looks like at this point.
The temptation is to get another guy in the portal, but I think you are right that chemistry and cultural fit make a big difference too. If you have Demin, Hall, and Diomande, not a lot of extra minutes to spread around. You might get a Tanner Toolson, or someone else who can add value as well, but Mboup is already here and will play with the previous six you already mentioned.
To integrate AJ, Staton, Mboup, and Diomande for next season, as well as Kozlowski - that is already a lot of roster change-up and different guys getting minutes for next year. It's going to take some time for it all to shake out.