Switching from PC to iMac in a few months - external hard drive question

Your PC cannot read or write a Mac drive without third-party software. The Mac can, natively, read from an NTFS formatted drive but it cannot write to one. You should be able to connect both external drives to the Mac, and copy your data from the NTFS drive to the HFS+ drive.

No worries! Would definitely recommend doing it all on your iMac.

I'd also suggest you read into the different file system formats macOS supports. If you don't plan on using the external hard-drive with older macOS machines, I would definitely recommend using APFS instead of HFS+, it's a much faster and efficient file system format. Keep in mind that APFS will not work with machines running macOS 10.12 or earlier.

For more information on file system formats see File system formats available in Disk Utility on Mac - Apple Support.

Best of luck!

Yeah APFS is relatively new, I don't know of many drives that ship with it (apart from Apple Mac products themselves) but it's super easy to format using Disk Utility, just make sure you format it before you put any content on it since Disk Utility will need to erase the drive to format it to APFS.

I'm unfamiliar with Glyph drives but definitely check if there are any consequences to reformatting them. Some external drives come with software you can use to manage the drives etc. and reformatting the drive may make it incompatible with the third-party software.

There are steps for how to Erase your drive and format it with APFS at Erase and reformat a storage device in Disk Utility on Mac - Apple Support if you are interested.

Assuming you have software on your Windows machine that allows it to read the HFS+ drive, you shouldn't have any issues.

As Kappy said, keep in mind macOS can still Read NTFS drives, just not write to them. This means if you wanted to be more certain the HFS+ would still work on your new iMac, you could always just wait for the iMac to arrive and then copy the files from your NTFS drive to the HFS+ drive using your new iMac.

Best of luck!