I agree with cyccomute that the Topeak bag is not the ideal touring/bike-packing choice. It might do the job if it's what you have. I love that bag as a commuting accessory. But as a touring accessory it weighs more with a lower capacity than actual panniers, and is not as robust as better touring gear. I find the rack is fine, though. I've taken plenty of trips using Ortleib panniers on my Topeak rack.
If you're no longer looking specifically at bike-packing, then a rack and pannier combination can be one of the most versatile set-ups and get you the most carrying capacity. But if you can travel light, and get all the required gear in a seat bag and handlebar roll, then I still think it's worth investigating for the weight savings, but I still prefer the versatility of a good, rear rack. I have abandoned my front rack in favor of a handlebar roll and frame bag, though. But if you need to carry a lot of gear, the four pannier set-up is still likely the most stable and easy to manage. But unless you have some extreme capacity needs, I wouldn't go for a front rack, rear rack, and frame bag, but that's more personal preference. For bikepacking gear, there are some great, cottage vendors, but I've been really happy with my Revelate gear.
https://www.revelatedesigns.com/ For traditional panniers, you'll find a variety of opinions, but Ortleib seems to be the most popular choice, and it's certainly my preference.