Do not plan on adding ram in the future; it may not be compatible.
Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
The internal workings are designed for the capacity of the kit.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards, can be very sensitive to this.
This is more difficult when more sticks are involved.
If you see a need for 32gb, buy it up front, or plan on replacing your initial purchase.
I3/i5 distinctions do not mean what they did in the past.
Most all include hyperthreading.
How many threads can you usefully use?
For most games, that is perhaps 4-6.
If your use is for apps that can multithread, that is where you should buy higher threaded processors.
Today, the ryzen units are good at that.
ryzen does not overclock significantly, even though their multipliers are unlocked.
For the most part, overclocks in the 4.3-4.5 are the best you can expect.
On intel, it is the K suffix processors that can get to 5.0.
If you are looking for a big processor boost for gaming, look at the i5-10600K and a z490 based motherboard.
Here is a review:
https://www.tomshardware.com/reviews/intel-core-i5-10600k-cpu-review