A bit late to the party, but generally, if the bridge has moveable saddles or moulded-on staggered saddle position, then the bridge will be installed flat to the pickup. It's generally only the pure rounded top stop-tailpieces used as a bridge types that are angled (or should be).

Whilst the JRM-1DC has a bolt-on neck and so you can adjust the angle with shims, the stock kit bridge is one of the tallest adjustable wrap-over bridges out there, and a lot of people seem to struggle with getting a low enough action without shimming the neck. So I'd be conscious of the bridge heights when making your selection. It may be best to wait until the kit arrives, then you can try the neck on and see what height you have to play with. I always think it best to avoid shimming if possible.

Because a dog-ear pickup isn't height adjustable, then the gap between it and the strings will be determined by the neck angle and action height. So using a shim and a tall bridge could move the pickup further from the strings resulting in a thinner sound and a lower output.

If you are planning to use an aftermarket pickup, then keep this in mind. There are less dog-ear P90s than soap bars available, but you normally get a choice of a bridge or neck position height. So again, it's best to see what sort of height requirement you need first before selecting a dog-ear. Of course, the rout should happily fit a soap-bar p90, which will give you height adjustment. As the JRM-1DC is more of a Melody Maker shape that a LP Jr, then either will look OK.

If a dog-ear sits too low, you can fit a spacer to raise it. For my GSJ-1 build, I made my own spacer from a fibreboard sheet, though you could equally use some black pickguard material. https://www.buildyourownguitar.com.a...l=1#post202403

But if a dog-ear is too high, there's almost nothing you can do to lower it apart from either a) insetting it into the top of the guitar or b) getting a lower dog-ear cover and bending the metal dog ears on the end of the pickup itself so that the pickup sits firmly against the top of the inside of the cover. You don't want a gap between the pickup and cover and you don't want the pickup sitting away from the top as it will be further from the strings and sound weaker, even if you do wind the pole pieces up so they fill the holes.

That SGJ-1 pickup probably ended up a little too close to the strings as it has a massive output and its easy to start distorting even a clean valve amp, but then again, it does clean up nicely (vintage tone pot connection wiring so no treble bleed capacitor needed) with the volume control.