I have found a smaller android tablet to be that happy balance of cost/weight/screen size that works well. My tablet doesnt have the phone thing, but I guess thats an option, although I know nothing of that aspect of them.
I used the tablet for what you are proposing--planning, researching, writing and relax time with wifi, and it worked well. Mine fit into my handlebar bag , with a hardcase cover on it, so that was a bonus, so maybe look into dimensions of bags and tablets , cuz its nice to always have valuables in the hbag to have with you always.
I could see how a light bluetooth keyboard would be nice, although it will take up some space in a pannier, it will be a lot lighter combined with a smaller tablet than a laptop perhaps--although there are those Chromebooks that are rather light, but I havent looked at them really.

totally off topic, but you've made it clear with your questions for setting up the Ogre and all other questions that you are all super keen to do a long extended trip, but consider perhaps before getting all the bells and whistles, to do some short trips to see if this whole bike touring thing is really your bag.


You havent mentioned (I dont think) if you have toured before, so perhaps space out your purchases a bit and see how it goes doing some test trips. At least with this electronic side of things, you could use what you have presently , and see with some test trips how much space you need for stuff, ie do you need to add a pack on top of your rear panniers, or reduce clothes, or whatever.
It is pretty hard to imagine this aspect of bike touring if you havent done it before, and then of course too the temperatures that you'll be encountering play a part in clothes, sleeping bag etc, and as we all know, budget comes into play and it makes sense to try to use the budget you have in the best way.

back to electronics.
for the budget side of things, I went with a very average tablet, I already had an android phone, I already had a point and shoot that I like and prefer to have a real camera for taking photos (as opposed to using phone or tablet) and also, I didnt want to spend a lot on a really nice tablet simply from a theft point of view.
Yes, a nicer newer tablet would have had a more powerful processor which would have been really nice for processing photos, which I do and is important to me, but again, I didnt want to be held up at gunpoint and lose a lot of money in a tablet (this last comment is specific to the trips I did, where I figured the chance of a holdup was possible, something I never would consider as a possibility in previous trips when travelling in N America or France or wherever--touch wood I guess)

anyway, so look into tablet sizes, weight , prices , tech aspect , storage space, and at the same time, think of what panniers you will have, and what handlebar bag for size considerations.
I personally have always kept all valuables in the hbag and bring it with me always, never leaving it on bike.
I also put an emphasis on waterproofness for panniers and hbag, so no concerns for wet electronics , which is worth it for me.