I think that is the primary issue with mixed level parties in a TTRPG system with tight math.
In the first case in PFS2e what you're most likely describing is some poor soul who brought a L1 character to a high tier table because its unlikely that you'll end up low tier with L4 characters. In that case them punching above 'their weight class' actually translates to fighting within tier as opposed to being dragged through the scenario on the backs of others and seriously risking death.
In the second case, as a Commander you can prep other tactics or take the shot at -5/-10 yourself. You aren't fixed to prepping it even if you selected it for your folio. I can't imagine this being a problem either because if the commander used this tactic a lot and was built around it you've actually effectively dropped party equivalent level by making them worse at the thing they built for.
In either case that specific reaction is actually 'rebalancing' the average party level closer to the average because a low level punches higher and higher level punches lower. That should give the GM some ability to properly establish a fair combat.
But ultimately. The best solution is to just use milestone leveling and keep everyone in the party the same level. Otherwise you run into similar issues on other classes that make you make DC checks against the highest level in the party like the bard's lingering composition. I think tieing in success or failure to other people's levels is counter productive to gameplay/flow and overall counterproductive to fun.
If you must have multilevel parties, I think the level spread needs to be minimized to 1 level gap at most. A 3 level gap as you described is just a shitty experience for everyone at the table. Either its balanced so the low level can contribute something (thus making combats way too easy for the higher levels) or even basic moderate combats will be like severe encounters for the low levels.
