A bit more background about your electronics experience would be helpful: Have you worked with FPGAs and microcontrollers before (using off-the-shelf development boards)? Have you done smaller circuit design and PCB layout projects? Can you solder well, and are confortable with SMD parts? What equipment do you have, or have access to -- specifically, do you have an oscilloscope, and what are its specs?
As others have said before: Unless you answer is a resounding "yes" to all the above, you should probably think about some easier projects to get you started. What you are proposing is a rather challenging project which requires the use of somewhat advanced tools amd techniques: FPGAs, oscilloscope and/or logic analyzer, PCB layout, soldering small-pitch SMD parts, flex PCB design and soldering, ...
EDIT: This is definitely a job for an FPGA, not a microcontroller. Trying some simpler projects with a small FPGA development board is a good first step. The two boards you mention in your second post are compact and affordable, but both use FPGAs from "new kid on the block" manufacturers which I can't say anything about. Gowin has certainly been mentioned on the forum, so maybe others can comment.
You will find that the development software is what really defines whether an FPGA is useful to you: Is it available for free at all (for non-commercial use)? Is decent documentation available? Have third-party tutorials and sample projects been published on the web? You may fare better with the etablished FPGA brands: Altera/Intel, Xilinx/AMD, Lattice.
All these software packages are complex beasts, and getting the hang of VHDL or Verilog programming (which looks like C, but is not the same at all) is a challenge per se. Hence, settling on an FPGA family, getting a cheap development board and the manufacturers' software, and starting to play around with something simple are my recommended first steps.