Hello
Sheet metal forming seems suitable for most of your parts visible in the picture.
For the central tube, I do not see any other appropriate technology, but know that it can be obtained in two ways: by extrusion of rectangular profile or by bending of sheet metal and welding, then sanded. These two processes are common among semi-finished product manufacturers, so it is recommended to inquire about existing standard profiles for the material that interests you. There are profiles that are very widespread and can be supplied regardless of the country of production, others that are rarer and may have to be manufactured on demand, therefore for a much higher price.
In any case, rectangular profiles are very common in the industry, and know that their longitudinal edges are almost always rounded.

As for solidity, it depends on the requested material, but in general it is almost as good as for a machined part, at least in steel.

I hope my answer can help you.