I find now with the Smart Stack, my most used complications are there on a swipe up. Also, I have changed to grid view for the apps and put my most used at the top, so a simple press of the crown gives me easy access. For me, I use a water intake tracker and a caffeine logger all day (well I have a no caffeine after 2pm rule lol) and those as well as workout, activity and weather are all I really need. I find it enables me to use a more minimal face.
I too, though, am undecided about what complication to use in the middle of the Radial. I have a shortcut to change it (well change whole face) depending on time of day. I am in UK, but work hybrid UK/US hours, so tend to work 12pm-8pm (give or take) during the week. I have home before 12, US Eastern time 12-8 and activity 8pm onwards (to remind me to close my rings!). They are all though a bit large as you say and I tried it without and it looked naked, so still undecided.