I love the Pyro RDTAs and have a few in my stockpile. My favorite RDTA is the WOTOFO "Faris", I've been using them for many years and have quite a few stockpiled. I do have a few Vapefly "Galaxies" in my stash that are single coil but I bought those for my better half in case the factory coils for her clearomizer disappear, never actually used one they're still in their sealed boxes. They have a small build chamber but are built for an adjustable tight draw geared more toward MTL vaping which is her preferred style. I don't know how loose of a draw their maximum setting would provide.
I have never filled my RDTAs through their fill ports. Mine are mounted on Eleaf "Pico squeeze 2" squonk mods so I just squeeze the silicone squonk bottle to fill the tank. This way I can refill my RDTA while driving down the road without even looking, takes about two seconds. Fortunately for me most (but not all) RDTAs come with factory 510 squonk pins, just have to install them.
The way you build and wick an RDTA determines if or how easy it will leak when turned on its side or upside down. Mine have never leaked when tipped over but they rarely get knocked over and usually aren't allowed to stay overturned for long periods of time. The only time I had a leak is when I over filled (over squonked) while not paying attention. I do mix my NETs 60/40 PG/VG so perhaps the viscosity works in my favor. I also fill the wick channels that run through the build deck full of wick, there's no empty space or voids.