The second company is in construction.
The third is design.
If you want to learn something, I suggest going to a design institute. Of course, the work of the design institute will be tiring. It's relatively easy to be Party A..
Do not recommend the second company. From the name, it should be a private enterprise. If you want to do construction, you should also go to a big company like China Railway Zhongjian.
On treatment: At first, it should be regarded as the highest in Party A, and the treatment of architecture and design is related to your work experience and qualifications. The initial salary is not high, and there will be a big increase in the future, while Party A's increase is small.