Best fuel additive for small engines?

I'm going to complicate my answer as much as I can. Here it goes.
I buy 5 gallon of premium fuel and mix stabil per their recommendation and 2oz of MMO in that. That I will run my 4 stroke lawn equipment.
Then I'll use that mix for my two stroke plus I do Stihl 2 stroke oil 2.6oz (1:50) and maybe .5oz (literally a splash) of MMO per gallon. In last 3 years of doing that I haven't had to take apart/clean/replace carb yet. Smells great when it burns and seems to burn good with no excessive smoke/soot.
I usually fill up a 5 gallon container and add a bottle of amsoil quickshot. That is what I fill my lawn mower and snowblower with. Supposed to clean the fuel system and has a stabilizer in there but it isn't considered for long term storage. I really should get some more stabil or something similar. The gas that is in my S4 has been in there for years. I do run it occassionally but I don't drive the car. I may have put some stabil in there before I stopped driving.
Regular unleaded gas from Quick Trip (no 10% Ethanol) , Stabil and a little MMO seems to work well for my mowers
Avgas 100ll has not let me down. Chainsaw with 40:1avgas mix set for two years and started second pull.
I've found SeaFoam works best for me. Engines run great and it is a fuel stabilizer.
SeaFoam contains up to 25% alcohol in it (from their safety data sheet). I don't put anything with alcohol in my engines since that voids warranties. Do you know something I don't about the warranties and why that wouldn't void it?
I put a splash of Berrymans Chemtool (don't bother measuring it) with 89 in every tank on the snowblower, lawn mower, etc. both start first pull after 16 years. The carbs are original and never been cleaned, taken apart or adjusted, they run perfectly. Proof enough for me.
I don't get all crazy measuring a ounce of this that and the other and mind friggin myself.