Hi Mike,
Answers in order:
Mike23 posted:those 3 you pictured 27” 34” and 54” Those were all considered low profile with a 7/16” height?
Yes, they are all "low profile" (i.e. 7/16) but to clarify: they are 27", 42", and 54". I assume 34" was a typo.
Edited To Add: Worth echoing Brianel's point: what you're calling "low profile" track is called "O27" track in this world; in other words, anything labeled "O27" track - regardless the diameter - is that "low profile" stuff you're asking about. And before you ask: yes, this means that you can purchase O27 O27 track (or O27 O42 track; and so on … fun, right? 
).
Mike23 posted:Then O gauge track with the higher profile also came in those same diameters, and other diameters?
Almost. Lionel O-gauge tubular track (i.e. "higher profile" track) was never made in a 27" diameter curve (to the best of my knowledge); however, they were made at 42" and 54" diameters. So, in those 2 diameters, you have both a "low" and "high" profile option from Lionel. For reference, here are the diameter options for O27 vs. O-gauge tubular track that should be helpful:
Mike23 posted:
if you were buying you’d have to be sure you were getting O34 low profile and not O34 high profile??
Yes at O42 and O54 diameters (see above) but not for others. But a caveat: Lionel never (to my knowledge) made O34 track and, of course, there's a whole world of O27 and O-gauge tubular track from other manufacturers I know nothing about, let alone whether they were made "high" or "low" profile.
But I would second Brianel: with a little effort most, if not all, of this tubular track can be made to work together.
- The Other Guy
For additional reference, here are the diameter options for Lionel O-gauge ("High Profile") tubular track:
- TOG
