Your answer raises more questions: 1. What kind of frames do you want to make and how many do you hope to produce? 2. Do you want to tig weld or braze your frames? 3. Are you just beginning to plan on building frames or do you have some experience?
My fixture is primarily designed to make custom steel frames one at a time. It is convenient to design the frame on the fixture and also check the accuracy of the miters. Most hobbyists put frames together by brazing with silver or bronze because it requires less equipment and training. They can make a good frame by taking more time. Tig welding is popular with professional builders because it is a fast and good way to put frames together. This method requires more elaborate and expensive machinery. The frames we make in Ukraine are mostly brass (actually bronze) brazed but are also silver brazed some places.
There are a variety of ways to build a frame. For example some builders make sub assemblies first (like putting the down tube and head tube together) and then combine the sub assemblies to make a complete frame. Others hold most of the frame tubes in a fixture and spot braze them together before brazing it into a complete frame outside of the fixture. How we choose to build a frame is based on how we learned and what equipment we use.
Like Andy says, most builders do not weld or braze a joint completely in a fixture. It is difficult to move the fixture to the best brazing or welding position at all times. It is much easier to move the frame while brazing when it is not held in a fixture. What we do is put a small spot (or spots) braze to hold the joint together and then braze (or weld) it free outside of the fixture. In between the spot brazing and complete brazing is an alignment check to make sure the tubes are in the same plane (not crooked on each other). This is the reason for the flat table. My fixture is designed to only spot braze a frame together because I don’t want to braze an entire frame in a fixture. There are some builders who will braze or weld a frame while it is held in a fixture (typically this is an upright fixture). I am not one of them. Sometimes on the rear triangle, I will braze a complete joint while it is in the fixture (for example brazing a seat stay to a dropout).
If a fixture is free standing it needs to be very accurately made. This can greatly increase the cost. The accuracy of my fixture is based on the flat table it lays on. This increases its accuracy and decreases its cost. I can easily adjust the position of the tubes up or down so they are all in the same plane based on the flat table and not dependent on the fixture.
The laser cutting and etching on my fixture is very well done. I had it made out of 5mm stainless steel flat stock instead of 6mm because it is ½ the cost. My fixture reflects they way I think and design and build frames. It works very well for me but it is not for everyone. This is why I asked you questions about your framebuilding plans. I can provide instructions in Ukraine about how to use the fixture and answer questions on how I build frames.