Match the pump to your tyre’s volume and required pressure. HV models use a wider barrel to move more air with each stroke. HP designs make higher pressures easier to reach. This distinction applies to both floor and hand pumps; the maximum pressure alone does not tell you how comfortable inflation will be.
Check the head’s compatibility with Presta or Schrader valves and any valve extenders you use. A smooth extender may need a different head from a threaded one. Replaceable hoses, gauges and seals can extend a pump’s useful life, so check whether those parts are available for the particular model before buying.
Seating a tubeless tyre on its rim is a separate task. An air reservoir such as the Topeak TubiBooster X stores air supplied by a floor pump and releases it rapidly into the tyre. It can complement a pump you already own. Consider whether you need this function and check reservoir, pump and valve compatibility.