Indeed, this forum was one of the things that attracted me to Line 6 in the first place. (Feel free click on my avatar at left for a bit of my background.)

I know of no other manufacturer that facilitates support to this extent.

Now, to the matters you've raised...

As far as I know, the six-channel handhelds for the XD-V30 and V35 both have Line 6's "58 model" representation of Shure's SM58 (the most widely used vocal mic on Planet Earth) permanently "switched on", as distinct from the variable modeling in Line 6's XD-V70 and V75 handhelds.

Some observations about Line 6's modeling and "pickup pattern" or polar response and proximity effect:

To my old ears, all of their models are very accurate representations of the "sound" (frequency and harmonic response) coming from cabled examples of the mics on which they're based, PROVIDED the Line 6's capsule is around a centimetre (1/2 an inch) from a given vocalist's lips.

Closer than that, or further away, the actual fidelity of the "copied" sound varies from model to model as the Line 6 capsule can only ever display its own "pickup pattern" which (of necessity) may resemble some "originals" more than others.

(While we're on the subject of those "originals", my observations regarding Line 6's accuracy are strictly in comparison to "fresh" or new examples of the originals, not the smoke, beer and shock affected veterans that populate many venues.)

I'm with you in finding that the "58-modeled" Line 6 has a "tighter" pickup pattern (and is, hence, less feedback-prone) than Shure's SM58, but this may be a mixed blessing, particularly when considering possible investment in a V75 handheld with a view to mounting the wireless version of Shure's own SM58 capsule.

I'm now talking about the "proximity effect" part of "pickup pattern".

Some vocalists who've "grown up" with Shure's SM58 (or another given type of directional vocal mic) will have "tailored" the subtleties of their entire expression around an instant variation in bass response being directly proportional to them varying their chosen mic's distance from their mouths.

A "master class" in such techniques is available from any YouTube clip of Ella FitzGerald in concert with her trusty (and immaculately looked after) SM58.

Now, as I've explained,  there's simply NO WAY that the Line 6 capsule can exactly emulate the proximity effects caused by the physical "build" of other capsules, so as to whether you'd be "...better off...leaving the mic as is..."

...the only viable answer to that question would be for you to try it out and see how happy the performer concerned is when actually "working" the mic.

As for me, ...I've yet to encounter a regular SM58 user who was other than delighted with the crystal-clear wireless freedom that I've offered.