@Murtuza Khoja
Welcome to BP, let me see if I can be of some help here. I have some YouTube videos that may help with some of your questions and always happy to have a call to dive a little deeper.
1. which development(s) tends to be the best for ROI/have the best occupancy rates?
There are more factors than just the community (#beds, level of theming, location to the amenities, style of home (single family, townhome, condo) and others) But I would strongly advise to stay within some of the same communities you mentioned like Storey Lake, Windsor Hills, Championsgate and a few others if cash flow is your goal. But it sounds like you should also balance your decision on what fits you and your families preference and style since you will be using it personally.
2. Which size of home is typically perform best on a cost benefit analysis?
This will also change from community to community. Some offerr condos, towns and sfr and all do well because they are closer to Disney. But since there are 10's of thousands of units here, bigger is typically better because there are fewer of them than smaller condos and towns. You can also personalize and theme larger homes better and seperate from the competition a bit.
3. What percentage of gross revenue does an owner typically keep if they do employ a property manager?
Most PM's here charge 15-20%, most are 20, but will depend on what services they offer. You'll likely want someone that can handle A to Z with marketing, pricing, cleaning, maintanence, decor, websites, reviews etc. Some will actually charge you to use your own unit, so be careful. Try not to get locked in too long
4. we're not necessarily looking to go "all out" in terms of theming, but if we did, what kind of revenue does that bring/ROI can you expect, and which Renos for theming are best to do from a cost-benefit analysis, and what do they typically cost?
Sorry, but this is another one that doesn't have a black and white answer. Some theming is basic and some is overdone, try to be unique or at least high quality, not a place you want to skimp. The better theming will attract a higher quality customer that understands the value. Theming can be $5-10,000 per bedroom (includes whole house decor, so a 5 bedroom could be $50,000 for the entire home furniture) depending on your imagination and quality. You should definately expect a good ROI, but I dont' have data to show how that would effect it would have on revenue. Making sure you are doing this in a house and community that will warrant it too.
4. If there are any owners on this forum that have any first-hand experience with STRs in the Kissimmee area? Would love any input you would have, especially from Canada, but anyone really.
I have helped dozens of buyers and sellers in these communities and can speak from both a Realtor and investor perspective, but not an owners view
5. I welcome any input from anyone who is knowledgeable in the area (comment not question, lol)
Wish you the best of luck, check out my Youtube channel and schedule a call if you like. My info is in my profile.