Why not just use the 10w30 EP if you don't want to use the high mileage? It's probably a better oil than the regular 10w30 m1 anyway. Or use any of the others as people have said it won't mind any of them in including 5w30.
My champion calls for 5w30 and I put 0w30 euro Pennzoil platinum in it after the break in, mainly because it can get pretty cold here in the winter and it's our backup if the power goes out.
A3/B3 are ACEA sequences for full SAPS passenger car oils with an HTHS viscosity at 150C above 3.5, API Resource Conserving and ILSAC have fuel economy requirements that essentially limit the HTHS viscosity at 150C to 3.2-3.3 max. The Mobil 1 High Mileage 10W30 is no longer a "thick" 30 grade it's a thinner 30 grade for better fuel economy. Most 30 grade oils on the market are of this variety unless they are Euro car oil that claims ACEA A3.B3,B4, or C3.
Yeah, you're overthinking it, but so are most of us that visit this site. Any of these are really good oils. The 0w40 is probably the best with the EP being second. High mileage is also good but more ideal for something that's older and starting to leak. Even that is mostly marketing as it may not help at all depending on the leaks.
It's all about the bottom number and what temps it's being stored in and started in. 5-30w in an attached garage no problem at zero F
Put the same unit in a shed at zero and without E start you're not going to pull it over fast enough to start it without 0-30w in it.
Real experience there with a BS powered 5600w unit.
Down south it's the high temps that are the worry.