I would suggest staying away from public trackers. Simply put, you are at a greater risk for harm in many ways. I am not saying you're exempt from that in a private tracker, but the likelihood is much lower. Check out the reviews index and you will find a plethora of information on the trackers. I would suggest starting out with ratio less tracker. Or one that is easy to keep.
Most seedboxes have pretty good connections these days. The good news is with the seedbox, you're not likely to have issues downloading or uploading, thus keeping ratios good. Consider that most of the seedboxes are a mixed bag. You may not get root access; thus, you can't install anything to compress files. Unlimited bandwidth is usually a bit more expensive. I have not surpassed my thresholds of 2TB upload with seedboxes.cc. My secondary seedbox is unlimited and unmetered, but I pay a pretty penny for that.I'm now on the road so don't have a persistent Internet connection and a seedbox is the obvious answer. I still have, and run, my VMware server but it's far from ideal with flaky WiFi. I don't use Plex and don't expect to be streaming. My current VM's have 300GB HDD's although my library is much larger. I'm thinking 300GB is OK and 500GB would be better. I think I want unlimited bandwidth... or at least I'm not aware of how much I use. 100Mbps seems slow and 1GbE seems desired, 10GbE is overkill. I do know Linux, I'm not an expert but I know my way around.
Private trackers are a mixed bag with regard to content. Depending on the tracker you will get things you can't find anywhere else. Each tracker offers something unique. Check out the open trackers section and you'll find a few that have open registration that might offer you what you're looking for in a tracker. Each one offers similar and different content, wider range of content because there is a sense of exclusivity with private trackers. Also, groups release to private trackers before it is found on public trackers (usually). Since you already have a VPN, use that for your traffic to move files from your seedbox to anything else you're needing the file to.Not sure if I need OpenVPN (Private Internet Access) on a seedbox. I wouldn't mind it but then I'd need special firewall rules (to only route torrent traffic over the tunnel and making sure SSH or similar access traffic always goes to the core machine). Not knowing private trackers nor having any accounts I imagine I'll be using public trackers. I'm assuming private trackers, assuming I could get one, would have a more limited library.
The seedbox OS varies, but it is essentially a linux box. You will pay for space, speed, and anonymity (in a sense). You will be limited based on what they allow you to install on the seedbox. Even with full root access, you will have a limitation as to what you can put on the box. I suggest you go here and you can get a good idea of the seedboxes out there and steer you in the right direction. Also, consider the following: you are sharing the server (as a whole) with other clients, you'll just be using a slot on their machine. Thus, they wont give you the keys to the kingdom, but they will do their best to keep you happy.It looks like I can get decent machines for $10-$15/Mo but there seems to be differences in pre-installed applications. On my VM's I just install whatever I'd like, whenever I'd like, so I don't know how using a seedbox changes that. I mean, is a seedbox more, or different, than just a Linux VM?
SO... in summation if it were me, doing it all over again:
1. VPN? Yes, NORDVPN or the like that works with openvpn.
2. Seedbox, yes. Seedbox with root access for certain apps.
3. 6TB to start with. Seedboxes tend to allow you to grow your library and require a great ratio - that means more files are downloaded, but you may not really want them, but you need them to prevent getting booted.
I hope this helps.
Cheers!