I dunno - those magnets looks small, so correct me if I am wrong, that would translate into a low QTS driver. Normally low QTS drivers (below 0.5) are not advisable for open baffle. You want something with a strong driver that can stop the driver movement in lieu of no enclosure assisting with cone resistance travel.
The nice thing about open baffle is it's easy to try them on a plankie to see how they perform. 8" drivers should make for a nice "full" sound. I would give them I try... who knows... though I am not betting on it

The Philips 9710 will make a good OB.
At the end of the day, experiment, learn and enjoy. When you arrive at the stage where you smile as a result of your efforts, it is very rewarding. You have to crawl before you can run.
Assisting them with a 12 or a 15 would definitely be advisable yes. I would not do it without it.
Something like the Hybrid series 12 or 15" would be a nice driver to use in an OB design.
https://www.soundselect.co.za/hybrid-12h200c-loose-speaker