I know Thomas treats defense as a suggestion. That's why he'll be used off the bench. He and Hield coming off the bench will be good for the second unit. In some situations he could even play with the starters, like Poole. If it worked for him even with his non-existent defense, I think it could work for Thomas too.
Johnson is an elite shooter with good size and athleticism. He's not bad defensively. Those skills will add much more to GSW than Kuminga's current ones. And on top of that, he wants a high salary. Let that be another team's problem.
Both shoot well from the free throw line, something that has been a problem for the team that is LAST in the league.
This way, GSW swaps out some redundant skills and actually adds those skills you really need: scoring and shooting. The playmaking that Podz brings is replaced by Beekman who is a much purer PG and a better defender.