I have just one external drive. One TB divided into three partitions. One for backups, one for storage and one for stuff.
I have a few more externals than that to store photos and videos from various family members, not to mention my music library, the OS drive and other backups, plus the skins I have collected over the years. However, to prevent slow boots, etc, mine are all inactive until required.
First option for upgrading any Laptop is more ram.
Second option is to dump platter drives for SSD.
Doing both will prolong the usable life of an older Laptop....and result in significantly less finger-tapping waiting for 'stuff' to happen...
That's fine if the laptop accepts more RAM. Shaunna's first laptop, a Compaq, didn't. It came with 4 Gb and that's all it would take. I tried inserting a stick of 8Gb of the same value, but the machine wouldn't boot until I put back the 4Gb stick. As for the SSD, well they weren't an option back then, and now she has an ASUS laptop that's quite zippy with 8Gb of RAM and a 120Gb SSD.
OS, Graphics proggies and FSX are all on a M.2 'drive' [think SSD on steroids]...
Depends on which type of M.2 you have: SATA; PCIe or NVME.... the NVME being the fastest as it uses more PCIe lanes and has higher read and write speeds.