I’d recommend using a 55 or 75 as the sump. No need for baffles. Just throw heaters and bio media in it and use a powerhead or two to keep the water circulating through the media. Use filter socks for mechanical. You can buy holders on Amazon for about $10-15 and then filter socks are about $5 each. If you setup a sump with filter socks and bio media, you will never go back to canisters for a large tank. The setup does take a bit longer, but the ease of maintenance is well worth it.
For my sump, I spend about a minute replacing filter socks every three days and throw the dirty ones in a bucket in my garage. When the bucket is full, I throw them in the washer with some bleach and they come out clean as new. The washing machine does all the work and I don’t have to take anything apart.