>>480032neat choice for the image!
>>480144Nothing wrong with using floats/bobbers in combination with a spinning reel (or any set-up really). If you're wanting to avoid bottom or just want your weight on the bottom but the hook/bait suspended definitely get yourself some. If you're intentionally trying to fish the bottom then you may need to invest in some weedless hooks or figure ways to rig your bait weedlessly.
As for crappie absolutely get yourself a small float. Crappie tend to look up for food rather than down so floating your bait is the way to go. Find a float sufficient to support the weight of your jig+bait or split-shot to hook+bait. A slip float/bobber + bobber stops would be ideal. The trick is to figure out what depth the crappie are at and adjust the line below the float/bobber to suspend your bait at that depth. Beyond that it's just a slow retrieve pausing occasionally to allow for a strike.
>>480062I don't know about the *BEST* battery you can get but you're likely going to be looking for a 12v battery of some kind. The more Amp Hours (AH) the longer the battery is going to last you before it is drained. If you want to save some money don't search specifically for a "Fish Finder Battery." You can search for that but also search for "Electric Scooter Battery", "Alarm Battery", "Wheelchair Battery", or even just "12V _blank_AH Battery" where _blank_ could be 4, 5, 7, or 9 just to rattle off some common AH ratings. Also do a search for "Kayak Fish Finder Battery Case" and you'll get some good ideas on how to keep it dry. A lot of folks will a hard-plastic dry-box/tackle box like what Plano and Flambeau make. They'll drill a hole for the leads and run the wires through a rubber grommet sealed with some marine goop, silicone sealant or the sort.
Can't recommend a fish finder unfortunately.
>>480161There are angler-model sit-ins but they're far less common than SOT anglers. I think this (
>>479325 ) might be theirs.