Hi Paul,
The size of the video file will largely depend on both the length of the video as well as the video resolution. Here's a video I posted recently of my new Allegheny & Pacific Railway Company, featuring Lionel's new Amtrak StationSounds diner (placed into service with my Atlas-O CZ cars) along with MTH's new Premier CP Holiday Train.
https://vimeo.com/255845744/33c4490f26
or the forum software can show an "embedded" video right here in a post (see below):
Vimeo is the video service I use in my professional photography business, and I prefer it over Youtube because Google knows enough about me from searches I do. I don't need Google to monitor everything else I might post on Youtube or send via a gmail email account. And trust me when I say most folks have no idea what Google is doing with the information you post or the emails you send. Google is a great and powerful search engine -- no doubt about that, but to deny its "Big Brother is Watching" potential is somewhat gullible in this day and age. They're not just hosting this stuff... they're always mining data from it.
There's a free, Vimeo Basic service... as well as Plus, Pro, and Business levels for fee. I just prefer Vimeo, because your stuff doesn't get lost amidst a sea of Youtube's video gibberish where hundreds of hours of video are posted per minute by everyone and their uncle nowadays.
The file I referenced above is 2.1GB in size, but it's also runs approximately 22 minutes... and is full 1080P, which I know a couple of folks here have enjoyed watching on their large-screen TV's at home. Right, Marty??? The full ProRes version of the video file is nearly 25GB in size on my computer hardrive, but there's no need to upload THAT size file to a video subscription service to get good-quality 540P, 720P or 1080P streaming files.
If you're capturing 4K video, there's no need to output a 4K movie -- and some subscription services don't support that anyway due to the resulting large file sizes. The other feature I like about Vimeo is their online player will choose the appropriate resolution of the video to "stream" based on the device where the video is being played. For example, there's seldom a need to stream a 1080P video to an iPhone. However, if you have a large tablet (or are viewing a video on your desktop PC or home's widescreen TV), then the Vimeo player can stream 1080P if the original video file was produced at that resolution level -- as long as your Internet connection can handle the HD bandwidth. Just select 1080P and click on the "fullscreen" icon in the lower-righthand portion of the video player's toolbar.
As Rich indicated, the proper way to share video is really to edit clips from your video capture device(s) with a Video Editor. If you have a Mac, Apple provides iMovie as a standard part of the Mac software suite that's already loaded on your computer. The above video was produced with iMovie from raw video clips I captured with a Canon EOS 80D camera. Video editors like iMovie are VERY powerful and convenient, given the fact you don't need to spend extra $$$ for them. You might find you need a few videos to get the hang of their nuances and to tap into all their features. Heck, I'm still discovering new jewels of info with each video I produce... and enjoying every part of the process. So they're worth it in my opinion, and there will be a learning curve for any video editor you choose to use. And if/when you outgrow iMovie's capabilities, there's always Final Cut Pro for Mac users. And Adobe Premiere Pro for PC users (and Mac users too).
There's a whole new world out there when learning to produce professional-quality video. So get you feet wet slowly, learn some good video capture techniques. And most important of all, have fun!!!
David