Note that low floor LRVs were originally developed to overcome a constraint common to street based systems, both legacy and newbuild, in most city streets, especially in older, heavily developed cities where streets are often quite narrow. A very high design bar is needed to make Low floor trams work. First of all, they all require the electrical control gear to be moved to the roof, and also require radically different bogie design. The bogies frames first of all are different, suspension is different, a high floor motor doesn't fit in a low floor bogey, and even the very wheelsets need to be different in order to fit a floor lower than the wheel hubs, which would require different fabrication jigs. And the only (ongoing) gain in all this redesign and fabrication jigs replacement is, well, level boarding capability in locations where high platforms don't fit.
The Edmonton LRT, Calgary C-train, Pittsburgh light rail, St. Louis metrolink, Tyne-and-Wear metro, most German stadtbahns and the KCR light rail in Hong Kong don't have stops/stations in locations like
here and thus able to avoid the constraints that low floor trams (and buses) were developed to address. Even on a completely new system where high platforms are possible in all locations, one would hope this advantage isn't squandered.
Nearly all high floor rail vehicles have standardised undercarriage designs, where the wheelbase of each bogey is at the absolute minimum length with a pivoting bogey under each end and articulated rolling stock having an additional bogey under each articulation.
But undercarriage designs vary widely among low floor trams, there are pivoting bogey designs with part high floor, fixed bogey designs with 95-100% low floor and a few 95-100% low floor designs with pivoting bogies, these still have raised aisles over the bogies, but with ramp access.
The Cobra trams in Zürich and the Viennese ULF have even more non-standard undercarriage designs, with an single wheelset under each end and joint.