I presume that this is a follow up to your other thread (Problems with AM386DX-40 chip)?
I believe that this should be your motherboard (which is a Biostar): http://arvutimuuseum.ee/th99/m/A-B/30648.htm
Based on the schematics, it would appear that the vendor either produced the motherboard with the 66 MHz crystal (and then provided a 33 MHz 386 CPU with it) or the 80 MHz crystal (with a 40 MHz 386 CPU) - so, I think it's safe to assume that this motherboard will work with a 40 MHz CPU if you swop out the 66 MHz crystal with an 80 MHz one.
To touch briefly on the CPU:
Back in the early 90's Cyrix introduced the 486SLC & 486DLC CPU's which were meant as an upgrade path for existing 386 owners of 386SX & 386DX CPU's respectively.
The benefit of these CPU's is that it offered a 1 KB level 1 cache, which provided improved performance over an existing 386 CPU (provided that the motherboard was "compatible" and the L1 cache was enabled).
You can read up more about it here: https://en.wikipedia.org/wiki/Cyrix_Cx486DLC & here: https://www.philscomputerlab.com/cyrix-486dlc.html
Just take note of the challenges and potential pitfalls. There is no guarantee that, with your particular motherboard, a Cyrix 486DLC (or one of its clones from Texas Instruments) will work with your motherboard.
However, should you be able to install a Cyrix 486DLC (not SLC) 40 MHz on this motherboard (with the L1 cache enabled), then you can expect performance more or less on par with that of a 486SX 33 MHz.
Since the first PC that I bought for myself was a Cyrix 486DLC 40 MHz, I can confirm the above.
FPU:
Unless you are planning using this PC for heavy duty CAD programs or running spreadsheets (like Excel or Lotus 1-2-3), you won't see any performance boost in your other applications.
The only two games that I'm aware of that makes use of an FPU (and that will run satisfactory on a fast 386) is SimCity & Falcon 3.0.
RAM:
I think that 8 MB should be sufficient for a 386.
Bear in mind that, back in those days, memory cost a fortune and most people only had 4 MB of RAM on their 386 PC's (and, as such, games were tailored to make use of that).
Cache:
Based on the schematics, the motherboard either supports 64k or 256k of cache.
If you can find the right chips (and depending on what settings your BIOS has for memory timings), increasing the cache to 256k should yield slightly faster performance.
I/O (HDD) Controller:
I'm not very knowledgeable when it comes to SCSI since, back in the day, I couldn't afford it myself.
I went straight from IDE, to VLB and then to PCI and so on.
However, it is my understanding that SCSI does yield better transfer rates but, it can also sometimes be a challenge to get up and running.
HDD:
Just bear in mind that your BIOS most definitely will have a limit in terms of the maximum HDD size that it will support (which in this case is 528 MB or 504 MiB).
This is more of a problem if you are using an IDE based HDD. I'm not 100 % sure how this impacts SCSI devices (which I think ran independently from the motherboard BIOS).
Graphics card:
Back in the day the Tseng Labs ET4000AX was probably one the most famous graphics chipsets (in terms of speed) on your ISA bus as it outperformed your competition like Trident.
However, I believe that some Cirrus Logics cards (like you CL-GD5422 chipsets) performs just as well. Finding later models on an 16-bit ISA card might prove a bit problematic.
I'm not sure how the ATI VGA Wonder card would compare to the above but, it will probably also depend on the particular chipset (model) of your card.
Sound card:
The SB AWE64 is probably a bit too "modern" for this type of CPU (a Sound Blaster Pro or compatible card is probably better suited).
However, on this motherboard, it will "behave" just like a regular AWE32 (Wavesynth/Waveguide is not supported on anything slower than a Pentium 90 MHz).
The benefit is that this card does not suffer form the so called MIDI hanging note bug and you can also use it for General MIDI based games.
However, the AWE64 uses Creative's CQM synthesis to "simulate" a real Yamaha OPL3 chip. Some people are not too bothered with it, other people dislike it.
I think that your greatest speed improvements will come from upgrading your CPU to a Cyrix 486DLC (once again, be aware of the challenges and pitfalls) and your graphics card.
However, some of these upgrades can be very costly these days due to their rarity.
Despite the above, even on my 486DLC 40 MHz, Doom 1 still runs a bit slow but much better than on a 386DX 40 MHz (I would recommend at least a 486DX2 66 MHz for that with VESA Local Bus graphics).