Transfer photos/videos from MacBook Pro to External Hard Drive (not iPhoto)

I've read all the other threads regarding how to transfer photos from iPhoto to an external hard drive (i.e., format your EHD to Mac OS Extended (Journaled)), however, I do not believe my situation applies.

In short, I download new photos/videos from my iPhone to my MacBook Pro twice - in two distinct methods. The first method (and the one I favor) is to use the Preview Application to download photos to the MyPictures folder. Once this is done, I revise the name of each photo so that I can tell not only the date but also the event. Once this is done, I then also download the same photos to my iPhoto Library via iPhoto but I don't make any revisions to the file names (I don't know why I continue to download photos into my iPhoto Library since I don't like iPhoto, but I guess I feel like it is a "backup" of sorts).

My problem now is that my internal hard drive is filling up and I must transfer some photos to an External Hard Drive (EHD). I thought the simplest solution was to transfer my iPhoto Library since I don't really use it anyway and many people advise to simply format my EHD to Mac OS Extended (Journaled). However, if I do that, my understanding is that I will not be able to then transfer the files to a PC, if I decide in the future to do so. The solution, as suggested by others, was to then format my EHD as "ExFAT". However, if I do that, my understanding is that iPhoto will not function properly.

So my questions include the following:

1. Is there any harm in simply deleting my entire iPhoto Library from my internal hard drive to free up space since I believe I have been downloading all my pictures in a separate location anyway (MyPictures folder)? Or will deleting my iPhoto Library somehow delete these other photos (even though they are not named similarly)?

2. If I decided that transferring my iPhoto Library to a Mac OS Extended (Journaled)-formatted EHD was the best solution, what would my options be if in the future I wanted to transfer the photos to a PC? Is that option lost forever? Or could I somehow transfer the photos from the EHD to the MacBook Pro, then re-format the EHD to ex-FAT, copy back the photos from the MacBook Pro to the ex-FAT-formatted EHD and then transfer the photos/videos to my PC? Is there an alternative better solution?

3. Any other suggestions?

Thank you