SSD drives "slow down". Yes. They begin at a million times faster than disk drives and stabilize at .999 million times faster. A non-issue in this context.
A RAM drive is not the solution.
- Page File in RAM: Reduces amount of available RAM, increasing need for page operation. Self defeating.
- Config/Ini files: Lost on power cycle. Yes, some apps keep config data in temp files.
- Browser cache/cookies: Lost on power cycle.
- Ad infinitum...
The difference between smooth and superfast is likely discernable only in benchmarking. Pragmatically, unless you are editing video or RAW images, there is such a thing as wasted RAM.
A 32-core CPU running at 3000+ TeraHZ with 4 thousand GB of DDR9 RAM won't give you a "superfast PC" if you have onboard video and your goal is to play Crysis.
My point being - the definition of superfast PC begins with - What do you want the PC to do? Remember, a PC is a set of peripherals wrapped around a microprocessor, enabling a user to do almost anything fairly well. In contrast, an XBox 360 is a set of peripherals wrapped around a microprocessor, enabling a user to do one thing very well.
And, in the PC environment, what is superfast today will not be superfast this time next year.
Having said that...
SSD or HDD - You need to modify your Win7 install files. Place User Profiles on a different drive than System Files. If you do this AFTER OS install, plenty of data continues to reside at C:\Users. Also, environment variables need to be changed to place TEMP off C:\Windows\Temp. The list goes on...