Are you asking about taking water out, or putting water back in? Or both?
I use different tools for different tanks in different locations.

• I have a small 7.5 gal cube in the upstairs office, I use a pitcher for water changes.
• In the basement, I have two racks with a total of ±20 tanks. For removing water, I use a 3/4 inch inside diameter clear vinyl hose with a few pieces of 3/4" CPVC (elbows etc) to hang it over the edge of the tank, it fills a 5 gallon pail in like 30 seconds. If any fish or fry get sucked up, I just net them out of the bucket. For filling the tanks back up, I like to use the most powerful pump I can that won't turn the tank into a whirlpool. I got an eheim compactON 3000 from a tent sale at Als for cheap (missing a few parts), and it works really well here (perfect for most applications, overpowered for some, and underpowered but still adequate for some). Best way I've found is to use a standard 1/2 inch vinyl hose attached to the pump, with a DIY spray wand type of thing on the tank end of the hose. Add a valve into your fill hose assembly and you can choke it down to whatever pressure works for you. My spray wand is made with 1/2 CPVC tube and fittings from Can Tire.

The pump specs you are looking for are head height and gph. Any good pump will chart these as a graph, and you buy something that will exceed the gph you're looking for at the desired head height.
Another tip: if you have a python, you can make better use of the tubing by connecting it with Gardena quick connect hose connectors. The 1/2 Gardena connectors for hose repair match perfectly to the 1/2" tubing that Python uses. Most of their 'female' connectors (what the plug part plugs into) have a check valve that I rip out to allow better flow.

 

Ideally for the emptying part. I have a python and can use that to fill.
Thanks for your suggestions