To answer this, you could of course read the documentation and figure out what’s the name of the respective properties of the TAPService object. In fact, you should set aside an hour or two to at least browse the documentation of PyVO if you use it regularly (as you should with any other library that you regularly use). However, in this case discovery with command line completion in ipython is legal; for instance,

In [3]: svc = dal.tap.TAPService("http://localhost:8080/tap")

In [4]: svc.availability<tab>
  svc.availability   svc.create_query   svc.run_async      svc.tables
  svc.available      svc.describe       svc.run_sync       svc.up_since
  svc.baseurl        svc.hardlimit      svc.search         svc.upload_methods
  svc.capabilities   svc.maxrec         svc.submit_job

It’s a reasonable guess that maxrec and hardlimit are what you’d be looking for in this case.

A program doing something like this for the whole VO would looks somewhat like this:

for access_url in registry.search(keyword="tgas", servicetype="database"):
  svc = TAPService(access_url)
  print(access_url, svc.maxrec, svc.hardlimit)