If the Cubs are going to play the "sellers, but still competitors" card, I think it comes down to two factors with Stroman and Bellinger:
Can the Cubs replace Stroman's spot in the rotation effectively? Wesneski probably has the inside track for this spot, but you're asking a lot of a guy who hasn't hit 100 IP in the majors yet. It's a huge roll of the dice, especially since I don't think it would be reasonable to hotshot the callups of guys like Brown, Wicks, and Horton. Unless the Cubs can pull off a trade for a SP with control, or they luck out with replacing Stroman in-house, trading Stroman would likely be a substantial net negative for 2023.
Can the Cubs get a better package of prospects than they'd get with a QO with Bellinger? There's been a lot of discussion about calling up PCA to replace Bellinger (not a fan), but I think the OF can be restructured in-house without the offense falling to pieces without Bellinger in the lineup.
Of course, if some team wants to be insane and do something like trade two Top 100 prospects for either, that would definitely alter the equation.