Hi and welcome to the forum
Your kitties sound like great little personalities!
In regard to the upset tummies I would recommend getting them tested for parasites especially TF before trying to switch diets as it can be quite common in Bengals, TF needs a PCR test that is sent of to a lab for diagnosis so you will probably have to specifically request that the vet includes this for you and doesn't just test for gardia etc.
A raw diet can be great but I would advise you to add taurine powder to their meals if you are planning to use only food from Raw to Go as they don't add it to their mixes and taurine is essential for cats to maintain a healthy heart.
Do you know if your kittens were raised in the home and had full access to all areas of the house? Inappropriate peeing can sometimes be due to being unfamiliar with soft furniture such as duvets and cushions which can feel similar to litter to kittens who have not come across them before. Alternatively it could be due to stress or a UTI, if your vet rules out an infection you could try a feliway diffuser and make sure that you thoroughly wash anywhere that has been weed on with an enzyme cleaner such as urine off to get rid of all of the smell. The ideal number of litter boxes is one more than the number of cats so in your case you should have 3 litter boxes available at all times. If she is over 4 months old it may even be due to her entering maturity, some Bengals can start callingas early as 4-5 months and the girls can spray as well as boys!
Please post lots of photos, we love pictures here!