How do I access my TS-233 over the internet?
Via MyQNAPcloud link.
Do you want a secure and safe solution or one that is open to hackers?
Start with some basics. What specifically are you trying to “access over the internet”? (web server, files, music, video, etc)
Do you have a router capable of running a free VPN Server? That is generally the best, safest, reliable and most secure way. It also depends on your ISP and what type of access you have, if you have DDNS.
Never forget to have a proper backup strategy, particularly if you are exposing anything to the internet.
You will need Tailscale/Wireguard running on a compatible router, a Raspberry Pi or the NAS itself. See https://www.reddit.com/r/qnap/comments/1mgd1az/tailscale_on_ts233/ for users that have done this.
Or any VPN server solution… Not limited to Tailscale/Wireguard 
Feel free to recommend them. That after all is what a forum is for.
Rather than say “Product X” is the solution, I prefer to say simply that a VPN server is the answer. Let the user decide based on what hardware they already have, and the knowledge that they have, how they want to proceed. That i why I started with asking for some basic information first
I don’t know what router they have, or what may or may not already be in place and running, but that or the other hardware you mentioned are certainly a starting point. Running on the NAS is self-defeating and not something I would ever suggest.
Whereas I prefer to suggest solutions based on my experience and why I listed a few options in terms of hardware. Other than a Wireguard based solution, what others do you believe are worth considering?
Whatever. Take a chill pill.
OP has abandoned this topic anyways
Hit and run
That is what I would recommend, especially with these temperatures.