The opportunity in the tax code available to those retiring in the year they turn 55, or older, is the ability to withdraw funds from the 401k of that company without penalty. I would consider this the "55 rule" you refer to, a critical component of my ER plans. Most 401K plans have this option as allowed in the tax code, you should confirm. The penalty free withdrawal WILL NOT be available if the proceeds are rolled over into an IRA, and do not apply to 401k funds from any prior employer. It may desirable to roll other 401k or IRA proceeds into the 401k plan from your final employer to access these funds at will. Another option to avoid early withdrawal penalties is under the 72t plan, which involves an RMD type calculation, and requires min 5 years of withdrawals. The penalty free 401k withdrawal provides much more flexibility and is an excellent option for ER. There is rarely any incentive for financial advisers to recommend this approach, most prefer to roll proceeds into and IRA they can manage for a fee.
Being ER'd with minimal regular income and the ability to draw on both taxable and tax deferred income provides some excellent tax savings opportunities. Sadly, there are few incentives or knowledgeable financial advisers to help with this. Typically, the optimal strategy is to convert tIRA to Roth IRA up to the top of the 15% tax bracket each year, or withdraw from tIRA/401k to this limit, or harvest capital gains. Another income ceiling to obtain ACA tax credits is typically slightly less than the top of the 15% bracket, (referred to as the ACA Cliff at 400% of the poverty level) and can provide additional tax savings.
After working for decades and paying taxes on steady income, it's difficult to grasp the tax saving opportunities in ER. There are many knowledgeable folks and posts here on the ER forum for these strategies. Perhaps some have found financial advisers or CPAs who can provide guidance like this for maximizing wealth in ER, I have not. I've spent the last year educating myself in preparation for ER. I encourage you to understand these strategies, and be sure any CFP or adviser would acknowledge (hopefully recommend) keeping 401k for penalty free access from 55- 59.5 (assuming the plan is not terrible), and provide Roth conversion projections similar to i-orp to minimize taxes and optimize wealth. The Boglehead post below opened my eyes to the new financial frontier of ER. Second link from Kitces illustrates the zero percent tax on qualified dividends and long term capital gains in the 15% bracket.
After you understand these concepts, the same strategies apply for the MAGI ceiling to receive ACA tax credits. If you find a professional who understands and will help execute these strategies for a reasonable cost, consider it. Otherwise, save the $15k annual cost and many thousands more in tax savings.
https://www.bogleheads.org/forum/viewtopic.php?t=87471
https://www.kitces.com/blog/underst...st-capital-gains-for-a-free-step-up-in-basis/