You will probably not be able to retrieve your data.
SSD TRIM instructs the SSD to wipe the actual blocks where data was situated on a delete command (instead of just marking them as empty). As such, your data is very likely permanently gone.
It doesn’t cost to try, of course, but the answer is likely no.
SSD speeds depend mostly on the size of a specific drive
It really isn't, though.
The physical structure the memory uses, the controller specs, and other factors are also involved, and have a more substantial impact on the speed of the drive.
Further, with an SSD you don't have access to the physical structure in the way you'd need to take advantage of any ...
If a flash drive starts with high speed and then goes down this is nothing unusual and in most cases has nothing to do with your PC. That your PC works correctly is shown by the good speed at the beginning.
There are multiple reasons for that behavior:
The internal cache of fast flash cells (SLC) is full and the other MLC/TLC/QLC cells are much slower
Windows creates a bunch of files (as required by UEFI) on the Efi System Partition (usually hidden in Windows) when installed in GPT/UEFI mode. When you clone the disk these files will not be present. Therefore the UEFI will not be able to access the Windows bootloader and will not boot.
The only solution is to clean install Windows on the new SSD. I am ...