That Tamron 150-600 sounds like the most versatile. I just love my 200-600 Sony lens. Another option that I use a lot is a good Tele-Converter. I have both a 1.4x and a 2x TC. They don't seem to lose any quality, but you do lose a stop of light for the 1.4 and 2 stops for the 2x, but these are comparatively inexpensive options. The 2x is really too much light loss for the 200-600 lens, unless shooting in extreme bright light, but I've had good luck using the 1.4 on it and use the 2x on my 100-400 lens to get that extra reach when the big lens not handy. They are light and very easy to drop in your pack or even pocket for that quick reach. Plus Topaz De-Noise and even Photoshop nowadays can work wonders on reducing noise on some of those noisy high ISO shots when needed.
The Tamron lens is great, but would be unusable with the teleconverter. When I used it in Africa, it was hard to get clear shots while zoomed all the way in because it closes down to f/6. It is a good budget telephoto lens tho.