If you have a roaming SIM card with enough data for use in China at a sensible cost along with a backup of an employer's VPN (assuming it's not blocked or hosted in Google cloud) then I wouldn't be faffing with a public VPN; it might be pragmatic to have pre-downloaded a VPN app or two just incase but not to take out a subscription.

It's true that employer VPNs, assuming they use SSL (as opposed to a known VPN protocol like IPSEC, PPTP, etc) will typically work from within China without VPN or roaming, but only up to a point. From my experience the firewall will look at traffic patterns and the technology will spot traffic that appears to be tunneled - very long lived TCP connections with either too much traffic, or periods with little or mo traffic but blips that look like keep-alive packets, and it will over time rate shape these to the point where they are inaccessible for a day or so from your China IP, or just superslow for an extended period of time. From my experience tunnelling through SSH (requires a bit more tech knowhow) has been been treated with less suspicion than SSL but do too much and the curtains eventually close.

​​​​​​In a pre-pandemic visit, I was able to do the graveyard overnight shift over several days on a data centre migration for my $dayjob in the UK from China just with my employers VPN on SSL and SSH using local broadband, with the backup of a roaming SIM card. YMMV...