Really? I’ve seen threads with people claiming to run dozens of services on it. What do you recommend instead, just any rpi OS and installing them like I would on regular linux?

if you plan on running portainer and then multiple services on your portainer. I honestly would not recommend rpi, and Im sorry its a nice little device but I dont think its very fast.
https://superuser.com/questions/1579497/how-does-a-raspberry-pi-4-truly-compare-against-a-modern-desktop-cpu

you can get some tiny SFF pc: https://www.ebay.com/itm/256201371098 that should have a tiny power consumption but 50x faster than rpi

see the benchmark: arm is raspberry pi https://www.cpubenchmark.net/compare/3213vs3917/Intel-i7-8700T-vs-ARM-Cortex-A72-4-Core-1500-MHz