The Cub mulching kit doesn't appear to have any baffles. Just the blades and blocking chute. The problem is that you get clippings from both cutting chambers discharged to a small area on the right side of the deck. And if it's wet you get a pile of mush and a plugged deck that pukes when you turn it off. Results will of course vary with conditions, but I don't recommend a mulch kit without baffles. If you're going to go that route I think an OCDC (remote controlled blocking plate) and mulching blades is the way to go. You can keep clippings out of areas you don't want them and mulch when conditions are suitable but open the deck up when necessary. Don't know if anyone makes one to fit though.I have a little bit of experience with mulching kits and 42" decks...... I had a Toro SS4225 with the recycler kit which is basically a new set of low lift/mulching blades (different in overall design and relatively flat sail) and baffles in the deck to push clippings down. The kit worked VERY WELL with few noticeable clippings. The secret to the mulching kit is to cut ONLY when the grass is dry, to never cut off more than 1/3 of the grass blade length, always run at full throttle and drive at half of maximum ground speed. On my Toro, which had the smart speed system, I could only mulch in the middle setting which was about 5mph. So, to answer your question, they can be good if they are proper mulch kits. The issue with stamped decks is that the clippings will still move from one side of the deck to the other. A fabricated deck with almost always have metal pieces that separate each blade into its own chamber (these are the best kinds of decks for mulching).
Yeah looks like an easy on/off mulch plug.
The mulching blades direct the cuttings upwards to be re-cut into smaller pieces. Mulching blades are designed to throw a lot less air with much flatter sails since the discharge is blocked. They often have a wavy edge profile which makes them a bit more challenging to sharpen.
Most of the time I run Gator G5 high lift mulching blades on my bigger mowers and mostly discharge. Mulching and bagging are both a pain if you're doing it on a large scale. The clippings with the G5 blades are pretty fine and there isn't much clumping when cutting wet. Personally I think that's the best way to go for the best balance of cut quality and clippings management. Discharging with high lift mulching blades. Mind you that's in my area with my grasses.
Changing blades isn't going to help with throwing grass into beds or onto hard surfaces though. I get grass into places it doesn't belong all the time and just hit it with my backpack blower. I throttle the mower down if I have to mow a narrow grassy strip with beds on both sides. I always start mowing by doing a couple laps around the borders of the lawn, patios and the driveway etc going clockwise. Just doing that makes a big difference. And I pay attention to which way I'm throwing on turns.
The wavy mulcher blades that come with most mulch kits, like I mentioned earlier, throw less air so the grass coming out the discharge doesn't have much force, so rather than being blown out 2 mower widths or so it all ends up near the deck and can cause windrows. Also, being that they're throwing less air, they're also providing less suction to stand up the grass for cutting, so cut quality can suffer.
Welcome.
Crazy question, what about getting a deck plug and not changing the blades to mulching blades?
Mulching blades are specifically designed to recirculate the clippings and cut the grass into finer pieces with it's longer edge and wavy design. With the plug in place, you help to further circulate the clippings inside the deck for additional cutting. The only reason why Gators and alike work without a plug on a commercial mower is because the blades are spinner quite a bit faster than on a consumer mower. High lift blades (or 2 in 1) as found on a riding mower will pack clipping all inside of the deck and create a lot of blowout with a plug in place.
Another type of mulch plug that is sometimes used is a screen over the discharge. This allows the air to escape but retains the clippings until they are small enough to exit. Typically this is a custom fabrication using expanded steel mesh or a similar material, but my uncle had a Deere walk-behind with a factory mulch kit that used a screen.