The first thing you need to do Dawg is ignore all the people, dealership or here, who tell you don't worry about having the warranty voided for modifications. Things have changed since 2016, and Harley signed a consent decree with the EPA that specifically requires them to void the warranty on any bike with illegal modifications. It's not the wink and nod system of the old days, and it has nothing to do with your favorite dealer "working with you". That dealer can easily find himself answering not only to H-D but the EPA itself, and the fines start at around $10k per violation per day. In other words, only truly ignorant dealership folks still sell illegal mods for 2017 and later bikes or claim those mods won't affect your warranty.
As for the severe engine issues on the M8's, read some of the threads around here on sumping. Heatwave and SDCVO have threads detailing their multiple failures with new replacement engines. Other forums have large numbers of reported failures as well, on base model 107's as well as 114 and 117 versions. Is it a 100% certain to fail issue? Not so far, but if you ride aggressively the odds of failures go way up. I seem to remember you weren't exactly a putt down the road at 2500 rpm kind of guy.
Welcome back. I'd recommend what some others have already told you, wait for the 2019 models. There are indications that Harley made some changes to the cases that may have finally fixed the root cause of the problem (see Heatwave's latest posts). It's highly unlikely Harley will go back and fix all the 2017 and 2018 bikes if it takes new cases or case modifications to really fix them.
JMHO - Jerry