IDK about guru but I just got my first sump after ten years of canister reefing, and the real reason I went sump was I wanted a planted marine tank with macros so it's 90% refugium rather then sump.
They worked fine and yes I use mechanical, biological and chemical filters.
Suggest bottom layer mechanical want least two layers a course and the very bottom and a finer layer on top.
second layer bio. I really adore the marinepure products they are leaps and bounds ahead of most of the other ring balls ect we have had in the past.
third layer I have chem. Polyfilter, some phosphate scrubber and leave room for a bag of carbon just in case but dont run it all the time.
Cleaning is important. Here is how I do it.
About every other water change(so once a month) I start the water change in my filter. Turn it off, lock the tubes so the water stays. Set the canister in a turkey pan(something to catch any over spill), pop the suction. All layers get put in a bucket. ALL the water in the canister gets dumped out, it gets rinsed out in the sink if there is stuff in there. The mechanical layer gets a good rinse out in tap water until it runs clear. chem is replaced or rinsed out as well, DONT rinse the bio layers(that will just kill them if you feel the need to slosh them do it in old tank water not tap). inspect polyfilter for any weird colors(signs of problems it just saved you from in your system) layers put back in, refill 98% with clean just mixed salt water(if you dont start with it filled be hells on the priming), reassembled but not turned on(least the ones I had would spray water everywhere if the DT water level got to low.)
Then I do my regular water change from the main tank(focused on sand cleaning but thats another topic) replace water, turn canister back on....3-5 priming pumps should do it. Do shake and tilt the canister some as there will be Some air in there this will get it out. Not including making the RO/DI water time ...and mixing the water up time....takes me maybe 45 mins.
I have the sunsun 304B next version up from your filter, they are beasts compared to other but especially for the prices. Be CAREFUL with the UV filter. If that tube cracks the pressure will force water up into the head of the unit and it will leak...slowly but a leaks a leak IT will also do this if you dont have a good water tight Vaseline seal on that tube. But it's one of the best I've had for priming, got a much more expensive one that my arm about falls off every time I have to restart it.