Platinum is the sweet spot and worth going for. Just get 30 nights from holding 2 credit cards. Stay only 20.

Titanium is nice and might have incremental benefits but I would never recommend doing a mattress run to achieve. Maybe 1-2 night mattress run so you can get a free night and higher points earning.

The material differences between platinum, Titanium and Ambassador are negligible.

I'd recommend 30 nights from credit card, 20 from stays and then switch to a different program when the properties are cheaper or better and stay at Marriott as needed if it is the better option. But mattress runs for Titanium aren't worth it