Filters are very important because they keep ammonia/nitrite at 0. So long as the filter you are using keeps ammonia/nitrite at 0 your frogs will be happy filtration wise(unless of course the current is too strong, noisy ect). There are many ways to filter a tank, and some people keep tanks without filters, and manage their ammonia/nitrite/nitrate without one.
How you filter your tank is completely up to you. I personally am not a fan of using chemical filtration such as seachem's matrix just because I'm not familiar with it. If best filter = low water flow, maybe a sponge filter is all you need.
What I would do is identify what you want in a filter, pick which filter fits those ideals, and research how those filters work. Canister filters are certainly nice, and there are a lot of options, but they can also be expensive, and there is the drawback of the potential for them to form anaerobic bacteria(low chance, but it has happened to me).
If it were me, I would probably stick with your current filter and add a sponge filter for supplementation. Sponge filters work great, and they are extremely low maintenance. Sponge filters are easy to make and pretty cheap.