My only concern is that I am saving a little over 50% of my income as it is and if I pushed almost all my savings into tax advantaged accounts I would not have access to it without penalty until 59 1/2. As I am only 25 and saving over 50% I will hopefully be FI and possibly FIRE well before 59 1/2.
This is just not true on the 59.5 part. Two ways to get to the money early:
1. Roth Conversion Pipeline
2. Substantially Equal Periodic Payments
So that's not something to worry too much over. And as to the SEP / 401K, it would seem easier to just use the SoloK, regardless of if you can have both or not.