Will setting up RAID 1 on secondary HDD(s) where games are installed affect performance? [closed]

From Wikipedia: https://en.wikipedia.org/wiki/Standard_RAID_levels

RAID 1

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Performance

Any read request can be serviced and handled by any drive in the array; thus, depending on the nature of I/O load, random read performance of a RAID 1 array may equal up to the sum of each member's performance,[a] while the write performance remains at the level of a single disk.

However, if disks with different speeds are used in a RAID 1 array, overall write performance is equal to the speed of the slowest disk. Synthetic benchmarks show varying levels of performance improvements when multiple HDDs or SSDs are used in a RAID 1 setup, compared with single-drive performance. However, some synthetic benchmarks also show a drop in performance for the same comparison.

This is mostly consistent with what you'll find across the web meaning, on average, you typically won't notice much of a change in performance under most circumstances.

There are some caveats depending on the implementation of RAID. For example software RAID can sometimes introduce additional CPU overhead which could effect other operations on the system, such as gaming.

TL;DR: Probably little if any impact, possibly faster reads, possibly slower writes.