All good advice;
Non Resistor plugs can be topped with NGK Resistor caps.
https://www.ngkntk.in/ngk-plug-caps/ The resistor does not have to be 'in the plug'.
Autolite 386 are a hot plug, I use them in a 7:1 Lycoming O-290 just fine. I wouldn't use them in my Lycoming O-360 8.5:1. They are an 18mm resistor plug, which is somewhat rare.
Extended tip plugs are awesome, the UREM37BY is supposed to be more likely to fire a poor mixture, and tolerate oil better because of it. I use them too.
If you can tolerate 14mm plug adapters, NGK BR9ES are good, including the exotic iridium BR9EIX tips if you want to pay more.
Next condition inspection I might try the NGK BPR9ES 2.5mm extended tip plugs....
I like to use automotive plugs on the top of my RV-8 because of the baffle clearance as you observed. I make up the plug leads from bulk 8.5mm MSD superconductor wire, and MSD plug boots.
NGK Resistor caps fit over 7mm wire, Taylor and Pertronix make excellent 7mm spiral core suppression wire.
I don't know if you need resistor plugs or resistor caps if you have spiral core wires.
My spark plug experience is limited to 7:1 Lycoming O-290 in my T-18, and an 8.5:1 Lycoming O-360 in my RV-8. My wife's RV-4 has Slick mags, aircraft plugs and a Marvel carb with VAN's air filter. I don't mess around with her plane.