RMDs and IRMAA don't seem to matter

A bit over a week ago I posted this regarding my prospects for FIRE where I asked, "Is it really this easy?" I got a lot of great feedback, most of which was, "Yes it is." One comment gave me pause though. The poster said that RMDs and IRMA may be problems for me.

First of all, IRMAA only seems to matter if I get Medicare part B and D. I can keep my current health coverage, which becomes secondary to Medicare after age 65. My current health coverage covers medication. If I keep this coverage and don't sign up for part B and D, will this be a non-issue?

Now for the RMDs it is more complicated, way too complicated for me to put me spreadsheet details here but in summary, it doesn't seem to matter. I looked at 2 different scenario paths, increasing my spendable money every year by inflation (nominal 3%), starting at about $130k (after tax), but not including healthcare, currently about $3k per year, continuing into retirement with the same plan.

In scenario 1, the market only did "ok" (6.44% per year), meaning that I was able to make my withdrawals but I died with 0 at age 100. In this scenario my normal withdrawals exceeded the RMDs so no extra money required. Note that even if I was at 0, I would still have SS (starting at 70) and my pension, which would be about $85k in today's dollars at 70 and decreasing to about $75k at 100 and $71k at 120, as my pension only has slight COLA.

In scenario 2, the market did "well" (7.3% per year). In this scenario I was required to take RMDs. Whatever was excess to my scheduled spend was then reinvested in a brokerage. In this scenario, although I had to withdraw more than my budget, my total balances continued to grow.