A few things to be aware of...
* Medicaid. While the ACA Marketplace plans use your full-year income to compute subsidies, Medicaid looks at your income on a month-to-month basis. For a single person this threshold is $1,677/month this year, will likely increase a bit in 2024 due to inflation. If you have individual months below this level in the recent past you could be put on Medicaid coverage when you go to sign up for insurance through the exchange, even if you expect your income to be higher than that on average over the next 12 months. This fact can take people by surprise! Some people want to be sure to avoid being on Medicaid, while others want to actively pursue it, and others are neutral on the matter. I'll leave it up to you to decide where you fall on that spectrum. If you want to avoid Medicaid you would be wise to generate income above that threshold each and every month. If you want to actively pursue Medicaid the strategy is generally to have income below the threshold most months. If you have an occasional month above the line (perhaps significantly so!) you would only get kicked off if you're above the line for two or more months in a row.
* Cost-sharing subsidies. You mentioned wanting to pursue a low-premium/high-deductible plan. This can often be the best choice for those in good health. However if you expect income above Medicaid thresholds but below double the poverty level (or roughly $29k next year for a single person) you might find that a silver plan with cost-sharing subsidies is the way to go. At that income level they swap out the regular silver plans (and only the silver plans) for ones with much lower deductibles and other out-of-pocket costs, for the same premium as the regular silver plan. You may find these to be a better overall deal than the higher-deductible bronze plans that don't get adjusted like this at lower incomes. The premium may be a bit higher than the cheapest bronze plan but the downside risk from out-of-pocket expenses would be significantly less.
For both of the above when I say "income" I mean the ACA MAGI, which is the adjusted gross income from your tax return plus any excluded foreign income, non-taxable interest, and nontaxable social security benefits you may have. You say you plan to live on $40k, but for taxable accounts in particular the amount you withdraw is not the same as the MAGI you'll recognize from that withdrawal. Any capital gains and dividends from that account will count toward MAGI, but any amount that is just the withdrawal of your cost basis doesn't count toward this number. Furthermore withdrawals from cash checking or savings accounts also don't count toward MAGI. For this reason you could easily withdraw $40k from these sources and have an income that would qualify you for one of the above income levels.
