I AM saying the companions are what introduced the imbalances and when you start learning the system, DON'T use the companions. I did use material from the companions initially and we found issues with them so weaned people off of them. (After RMCIII came out, I stopped buying companions. RMCI had some balance issues, RMCII had a lot and RMCIII was pretty much unuseable.)
Start with RMC, learn it. Then add stuff that you think will work in your world.
RMSS/RMFRP took a lot of the bad stuff from the RM2 expansions and incorporated them. Additionally, a first level character in RMC and RMSS are a totally different breed. They front end loaded characters in RMSS so you have higher starting OB, PP, etc and aren't going to improve a lot over time, in RM2/RMC, you start low and build up.
Honestly, in RMSS, you aren't 'first level" when you start. You have completed adolescence, apprenticeship and have a bit of military service (or its equivalent) behind you.