There are some models without the typical ISA interface but a proprietary connector instead.

You should be able to use an 8-bit VGA card in any Tandy 1000 except the original 1000/A/HD, as the internal video cannot be disabled, or the 1000 RLX/RSX, which have VGA on the motherboard. The 1000EX/HX use pins instead of slots, so an adapter will have to be hand-made.

There are some, usually early 16-bit VGA cards that will work in an 8-bit slot, these should be good for a Tandy. Beware of boards longer than 10", as they will not fit inside the Tandy case.

All Tandys can have their RAM expanded to 640KB, but the 1000/A/HD/EX/HX require special Tandy memory upgrade boards. The rest are upgradeable on the motherboard.

If you have a VGA card installed, you could use it with a flat panel that has a VGA or DVI-I or DVI-A input.

You can use an 8-bit sound blaster in a 1000, with its has two serious drawbacks. First, if you have a Tandy TL/RL/SL/RLX/RSX,you will need to use a Sound Blaster Pro. Sound Blasters 1.0/1.5/2.0 only allow use of DMA1, which the Tandy DAC also uses. Things will freeze if your game tries to use digital sound if both are installed. So you will need a Sound Blaster Pro and need to set it to DMA3.

Second, if you want to use a joystick, on the 1000/A/HD/EX/HX/SX/TX, you will have to use the Tandy proprietary ports. Unlike the ports of the TL/RL/SL/RLX/RSX, these cannot be disabled. Disable the joystick port on the Sound Blaster by setting the appropriate jumper.