I actually did an AC with TopScore for a non-law graduate role. I think the platform is easy to use, the documents for the written task will be opened in separate tabs, so it will be like different pages / tabs shown on your Chrome.
The only annoying part is that there isn't a timer on the page. It only shows the end time e.g. 11:30am, but that was not accurate in the sense that it won't close sharp at 11:30am, but suddenly close like maybe 2 or 3 minutes later. I think that buffer time is given for some final proof-reading, but when I tried to type something more, it just closed down randomly 🥲
Other than the timer thing, I think the platform is fine. Good luck with your AC!