You are limited in the overhead sounds like. I did a lot of research on lifts and the foreign made, most of them, are rated for more than they can actually do. There are videos of them placing steel plates on the lifts and them folding up when it is the advertised capacity. There are lots of videos on the net showing accidents.
I am probably going with a 2 post lift just for ability to get to everything better. Yes you can add extras so you can take the tires off and do stuff but just not as easy to get to things.
Talked with people that use them every day and they say no to 4 post unless you want to stack store cars and you can get the really cheap ones for that.
On the floor mount. They all say you can drill and use drive in concrete bolts. I am not. I am going to do a two stage pour on the garage and when they put the J bolts in for the building uprights they will also put in J bolts with welded re-bar so there is no way they can pull out. Too many videos out there of units folding, bolts pulling out and falling. Not something someone told me but there are videos online.
I have lost the name in my mind of the company in Texas that actually builds their lifts in the U.S. I need to go back in my records and look that up and add to the post. The foreign lifts are made from much less strength steel. Hot rolled steel can vary in yield strength from 20,000 to 100,000 lbs. so there can be huge differences even when they use the same thickness.
I know we all want the least cost we can get but you are going to be under there and your baby will be on it. How the electrical or hydraulics are built can be cheap also. Find a garage that has been using what you are looking at and go talk to someone that has put them to the test. Go look at some of the horror videos online. Some are in big car dealers. The actual testing of lifts are on there and the arms twist and fail when they put the advertised weight on them.
I worked in China for 16 months in a shop and I know how they like to use the minimum they can get by with, bolts, cables, hoses, valves, materials, welding, wiring, motors. They will use the minimum every time not much safety margin if any. Heck our welder did not wear a helmet. I ask one of the guys that could speak English to ask him if his eyes did not hurt and he said no. He would weld 8 hours a day building tables, racks and die stands and only had a piece of cardboard with a hole to look through. The cardboard kept the spatter off his face.
I don't trust them either, lol.
David