Is OS Monterey will slow my iMac 2017

macOS Monterey should not be any slower than any previous version of macOS. If you're running macOS Big Sur, most of the interface will look the same, so you'll barely notice a difference.

You can follow this guide to upgrade to macOS Monterey, but if you're using macOS Big Sur, I would wait for a later update to macOS Monterey.

Upgrade to macOS Monterey - Official Apple Support

What can slow a computer down (other than hardware issues) are unnecessary programs running in the background (like virus scanners, clean-up apps etc). In addition, having too many windows left open after finishing using apps. It is good practice before upgrading the OS to get rid of any redundant programs. If you can, do a clean install of the OS and later only install the latest version of apps essential for daily use.

Note that if replaced that Apple drives or they are not working you will not be able to install Monterey. The Monterey upgrade for your model Mac and some others too include an update to the mac's firmware and the installer checks if you have working Apple drive and if not terminates the Monterey install.

Tips Monterey Upgrade 

The Hardware on the computer could be a factor on slowing down the performance. Fusion drive tend to be a factor even if the Rotational Drive is the 7200 RPM type.