Is it wise for me to just focus on VWRA for now, or can I diversify into other ETFs?

You can but, one thing to note would be VWRA is pretty heavy on the US already (since the US produces a lot of stuff) so adding US ETFs would be overweight on US companies in particular. As such, you should only do so if, you're bullish on the US companies in the ETF you chose, over other regions.

If you wish to diversify, some people do recommend emerging market ETFs (although they have underperformed in recent memory). Another way would be through thematic ETFs (e.g, green energy, semiconductors etc.). Do be careful with this though as a sector doing well might not always mean that the ETF does well with it too (especially if many of the companies inside are very highly valued at the moment, looking at you EV sector...).​​​