I tend to think of myself as a militant 'low-ender' so I have a particular, not to say peculiar, perspective.
That said a reason for building a system around Lynx converters would have very little to do with extreme fold back latency. As has been pointed out analog monitoring always beats digital fold/loop back by definition and drivers, specifics of Hard Drives & peculiarities of OS (& in my experience Win keeps getting worse and worse for audio production) have more impact on loop back latency then a specific bit of hardware (once you cross a certain minimum threshold)
You could easily build a Lynx system with which you could live for a considerable time (as long as you could refrain from unreasoned, random upgrades). Lynx have been at the top of the prosumer food chain for a long time.
I've been doing punch ins & overdubs since the 2 track 'sound on sound', 'sound with sound' days and no system I've ever used gets you to 0 latency. And in approaching that meta-goal there are typically compromises that will impact work flow significantly.
And for OPs stated goals the recording environment is going to be far more of a challenging variable then difference between a RME UFX or Lynx PCI card.
How significantly upscale mic pres are to signal chain is also influenced by factors more significant then any bit of gear. E.G. room & mics. That said whether it's subjective or not I can detect a difference between my 512c's and the CAPI 312s. Not so much that I wont buy more of the Classic API's (V28 I thick will be the new one) faster then filling a rack with 512c's but was surprised as recently as a month ago by an acoustic guitar track that I had expected to be recorded using a different pre (Daking or DAV don't remember now) used the 512c . . . & without being able to accurately describe 'how' the sound differed from what I expected to hear (and would not have known that I expected to hear anything other then that it would be OK in the mix) . . . but hearing the Martin D35 via a pair of KSM 184s through the 512c's brought a spontaneous smile to my lips.
I am also OK using the Vintech Neve-esque options but do tend to think I hear a difference, subjective or not, in carnhill Xfrs powered via 24 v. vs. 18v. So while my approach was to build the mic cabinet (slowly) first (& have been far too transient to ever do a room the way I might want) even for my location recording where the clients could care less I'm happy to use the lunchbox format for 'better' pres (& stuff) in a relatively portable format. Whether I'm deluding myself of not auditioning pre's keeps the gear lust in check.