What make/model is your sub? Many active subs have all the active crossovers you need built in. There are pros and cons with every type of crossover filter, whether active, passive, internal, or external. There’s not a set of absolutes that apply to all situations. Proper sub integration is a variable that’s unique to each situation - the room is significant factor, as are all the settings of the low pass frequency, gain settings, any high pass settings that might be applied to your mains, along with how all that works with the rest of the system in your room. Overcoming the particulars of your room with proper adjustments is more important than the type of filter or it’s proximity to the sub. There are DIY programs that can be used to help make adjustments, or you can do it by ear to suit your tastes. There’s really no wrong way to do it if you’re happy, and aren’t damaging anything.
My view is that a "sub" woofer should simply be reinforcement of the lowest frequencies that the main speakers might struggle with in a given room. Many, many subs are setup poorly IMO, and treated as a featured component with the gain set too high relative to the output of the mains, and low pass frequencies set too high where they affect the vocal range (above 70hz), and the subs end up dominating everything else in the blend. I prefer to set the low pass filter in the 40-50hz range so that the sub only augments the bass my main speakers produce, set the gain level so that it’s barely noticeable except for on bass heavy passages, and I run the main speakers full range because I prefer not to send the signal that goes to my main speakers through the filters of the sub, but that’s a matter preference based on the specifics of my situation.
Some speakers may respond well to having the low bass filtered from the mains via a high pass crossover filter (whether active or passive, or internal or external), and handled solely by the sub, but that’s also a variable, and there’s potential for degrading the main signal depending on how that filtering is done, quality of parts, etc. Many variables, many matters of preference, YMMV..