Lots of people use 120GB and 240GB SSD products. For those with <= 120GB, the upgrade to 240GB is advisable. The reason for using at least 240GB is due to Windows updates. The low cost Kingston A400 120GB SATA SSD is common with refurbished laptops however more recently the 240GB SSD is now becoming more common with the added capacity being uses as a feature. The Kingston A400 top out at 960GB.
After using the 120GB SSD for some time it seems to be running out of space all the time. This is due to the Windows update files cluttering up the SSD. The browser cache with Edge and Chrome are fairly well managed but they also use some SSD space.
Disk Cleanup can get rid of the fluff and free up a lot of space but over time it will be back to square one.Adopting a 480GB SSD is now moving into the mainstream. Prices for SSD have fallen substantially. The Kingston A400 480GB sells for 69.99 in Canada with free shipping. The KIngston A400 960GB SSD sells for 129.99 with free shipping.
Cleanup System Files will get rig of Windows Update components and old installations etc.
Amazon and NewEgg still have a lot of obsolete small capacity SSD products at prices per GB that are not very attractive. The 480GB SSD has lots of room for several games which makes it a much better value.
For the M.2 slot there is a lot of competition in the 2TB capacity. Prices start at $254 and up. The Samsung 980 PRO 2TB is double the cost of the lowest price SSD. 4TB M.2 SSD start at $759 which is brutal costs per GB. Prices for 2TB are eroding and by 2022 they should be moving closer to mainstream pricing.
With a 960GB or larger SSD, disk cleanup is not generally necessary.