The seat in the 650 does slope forward but whether that's annoying to you or not is a personal preference. I've been riding with the stock setup and I'm over 40k miles.
Bought a bigger windscreen but that's cause I'm 6'3.
Pegs, handlebars, all stock. Heated grips are great in colder climate.
All in all, the V650's ergos are pretty good for taller people straight from the factory.
Now, if you've been riding a KLR and contemplating a V300, you might be thinking of going off-road, is that correct? In that case, the 650 won't be great. It's a 100% road bike, with just a bit of a lifted suspension for comfort - like a crossover car
Some people have adapted the 650 for ADV use, even going as far as installing a bigger front wheel, lifting the fender, etc. but you'd be doing extra work and spending extra $, might just get a more off-road oriented bike. The 300X is, I hear, much easier to handle offroad.