Microsoft Paint, mostly. For layouts, I copy an image of graph paper from the internet and draw layouts on it using the simple tools available in Microsoft Paint.

For 3D images, I find a picture on the internet of something similar to what I'm thinking and doctor it using Paint to look as close to what I'm thinking as possible. The doctoring looks jenky, but it gives me plenty good sense of how my idea would look in real life. I also make mood boards with Paint.

I did just learn how to use Sketchup to make far less jenky 3D layouts, but I don't and won't use it nearly so often as Paint. Takes way more time and is kind of a pain and buggy, so I only use it for final final layouts. Or if someone here is particularly struggling with envisioning things from a 2D plan.

There is no software on earth that is good for color comparison. Colors look different on every single computer screen. If you are trying to pick colors, get physical samples of everything, and view them together under the actual real lighting conditions of the room you are considering them for and at different times of day in that room.

I used the Ikea software...it wasn't completely perfect because we did not use their cabinets but it really helped get a good idea of what I was thinking.

I use the industry standard, 20/20. But to alter others posted layouts on here, Paint works just fine. I need something for a tablet though and haven't found anything non wonky.

On my Mac I use the Ikea planner which is much improved now for the past 3 weeks :-). I use "Grab" to take screenshots of the bird's eye views and safe them as jpg or png, which I then doctor while opening them in "Preview", which pretty much lets me do whatever I want to with them. In Preview it's much faster to make changes on an existing plan than to keep using the Ikea planner, other 20/20 software or sketchup. I do not use preview much to alter screenshots of elevations.

LWO-Not sure what you need from a tablet app? what you want it to do?

There is "Room Planner" from Chief Architect for both iOS and Android. Not going to be able to get it into 2020, but then only thing that really imports into it is Envisioneer. (I have but rarely use either, mostly use Chief) It's cheap enough it may suit some users here on the forum.

You can do screen shots and save, don't know if it prints? SO that can give you a way to trace something in 2020. Room Planner files can be imported by Chief and some Home Designer products.

I've considered "room planner" mostly because it can read directly from a laser. Just not convinced the method suits my needs.

IF you only need to mark up plans and elevations Bluebeam PDF Revu has an iPad app that does that. I use the full version but have not tried the tablet one. One of my favorite tools.

I almost bought an iThingie just to use these. But again, not so sure it makes sense given the rest of what we use. Really curious how you see using a tablet app?

For the tablet app, I'd like something that I can jot field notes or lines in over a JPEG of either a 2030 screen shot or elevation. Or someone's layout on here.

I have a iPhone and use an app similar to that now, but the screen is too small and my fingers too big. And my eyes too bad. Basically Paint for Android or IOS.

My Android tablet just died (the USB port pins fell apart and no one seems to have the skill to solder A new one for I t) so I'm looking at a new to me something. A strong recommendation for a good app that does that well would sway me one way or the other.

Or, I might go to the dark side and do a Surface. That's probably more than I want to spend though. And I already have a laptop with 2020 and paint and everything else imaginable. Lightweight portability and a large enough screen for the blind person that I am are the reasons that I use a tablet more than even that stupid bigger sized iPhone 6.

LWO- take a look at the Bluebeam app I mentioned- only available for iPad (which I consider the dark side :) I almost got an iPad mini just to use it. I still might but tech can simply be a bottomless pit and I always have a list.

You can download a trial of the full BB (standard -no need for CAD) version on your laptop to get some idea of using it. Be a good idea to check the iPad resources they list to see which tools work and which don't before taking the plunge. Take a look at the sequence tools- great for numbering cabinets on pdfs from 2020 floor plans.

Overall you can: markup, measure, place shapes, places appliances, doors, windows (to scale) draw lines, make notes, and insert an image. Getting an image to scale takes a little practice/math, measuring isn't too hard. The iPad app also imports photos and video taken with the tablet which is one of the big reasons I consider it.

I kicked around a Surface Pro- I travel a lot and was looking to cut some of the weight. It's easy enough for me to move the Chief license. 2020 is a pain but I don't use it enough to care :) I have a 1.5 lb USB monitor for a second screen that will work with it. Transferring a Bluebeam license between machines is a pain and I couldn't live without it. A full version is $250 and (and I already have two), tack that onto an i7 Surface..$$$. I'd just as soon put 2 grand into an upcoming Skylake laptop. So I shelved my Briggs and Reilly bag and got a back pack for now; saved a few pounds and my back :)