First, for both HF and VHF/UHF, forget the idea of moving the same rig in and out of the house, into the vehicle
and back. It just doesn't work out.
HF is very difficult to get a signal out when operating mobile. I would leave that until later and just leave the HF
rig in the house.
VHF/UHF, buy two identical rigs, program the same but for power output. All mobile channels should be programmed
full power. It is easy enough to reduce power if you know you are close to a repeater, but you want to start off full
power. For your shack, where you know the range to various repeaters, you can program it such that close repeaters
are set to low power. Also, it takes a lot less power for an antenna on your roof top or a mast than the antenna on
your vehicle for the same effective range. I have a repeater in the next town set for 65 watts in my vehicle, but my
base rig, for that same repeater, 5 watts.
You want to get used to operating the mobile rig without having to look things up in the manual. And as much as
possible, without having to look at the rig. Get used to its operation at home when you are not distracted by driving,
or more importantly, when operating the radio will not distract you from driving. DO NOT, for now, install a rig in
your vehicle. Learn to operate at home, both the radio, and you. When you put a radio in the vehicle, buy an
identical radio for that purpose.
For an HF rig, buy a 100 w rig. QRP (low power, under 5 watts) can be fun and all, backpacking, camping, but can
be frustrating, too. For your base rig 100 watts.
Power is less important for VHF/UHF. Antenna height is a much bigger factor. A 50 watt rig is more than enough
for mobile.
You need a tuner for your HF rig. "You don't need a tuner, just a resonant antenna." Good theory, like needing only
a single shot rifle if you are a good shot. But you can operate on a lot of RF real estate where the antenna is less
resonant, or not resonant at all with a tuner. Lack of tuner limits you, and a tuner does not "waste power" to a degree
where it makes any difference to the station called. Automatic tuners are quick and effective, a manual tuner is no
more efficient. My experience, if an LDG tuner won't find a tuning solution for a particular antenna and frequency, then
a manual tuner will not either. I have both, and have used them side by side. I prefer my LDG auto tuners.
"Shack-in-a-box" radios (HF/VHF/UHF) such as the FT-857, FT-897 don't do anything particularly well. I found I really
did need two separate radios, one for HF, one for UHF/VHF. They are used differently. HF you dial around the bands,
look for a contact, etc. VHF/UHF is channelized, and much operation on repeaters. These radios are left on one
frequency to monitor, and many times you may be working on HF while monitoring a local VHF repeater with the other
rig. An all-in-one radio can't do this.
Just a few thoughts and suggestions.