ok, update. The issue seems to have nothing to do with loading a large session. RStudio preview is locking up on me after a few minutes of use regardless of what i do. Current testing seems to indicate that it may have to do with using Solarized Dark (strange...). I'll use for a while without it and will report back.
update: nope, took a while longer, but it hung on me again without any theme applied and after deleting the rstudio-desktop and .rproj_user folders.
update2: confirmed that the hang keeps happening no matter what i do. a little bit of usage accelerates the hang; without usage, i haven't seen it hang yet. When it hangs, the upper menu is working, but nothing in the panes will take input. The cursor turns into hands, etc, when moving over objects in the environment pane. But clicking on those objects doesn't do anything. The rstudio window doesn't redraw when resizing (e.g. i size it down then up again, and the occluded areas are just blank). Logs are empty, diagnostics -> reload UI doesn't do anything. My guess is that the chromium system is hanging on my machine for some reason. Not sure how to debug from here...