Hi som99, I have two Amiga 600s and I use one of them as my main system every day, so I can tell you the honest truth here and not just speculate. Sometimes people try to help, but they might just end up confusing you more with misinformation and false memories.
Running WHDLoad games with only 2MB ChipRAM on an A600 is next to impossible. You will barely get any games to work at all from Workbench, and only a few will run if you boot with no Startup-Sequence, but since you're going to have a 2MB SRAM card as well, this won't be a problem for you. Still, not all WHDLoad games will run, many seem to have incompatibility problems with this setup (I have a 2MB+2MB A600 also). I have had many games crash when I tried to save them, and many have problems with the second fire button. Many can't be quit with the QuitKey, although rebooting the A600 doesn't take that long anyway. Once you filter out the games that won't work properly, you'll still have hundreds to choose from, and the ones that don't work might just have to be run from floppy disk.
If you get an Indivision ECS, it needs to be plugged into the extra socket that's attached to the A603, but not the Clockport. The Clockport will still be free for you to add another expansion card, like USB, 16bit Sound, Fast Serial or MP3 decoder. The Indivision will have a VGA plug on it, which you will have to cut a hole and mount somewhere on your A600's case, or have the ribbon hanging out somewhere with the plug on the end. Your monitor will then plug into this, and all Amiga screenmodes will be scandoubled to display on your monitor. The added advantage of using an Indivision over a VGA converter box is that you get the sharpest output possible, you never get Interlace flicker anymore, and you can run your Workbench in 800x600 in 16 colours (which doesn't look as bad as it sounds if you do it right).
Your Amiga itself will not be limited to 16 colours, not in low-res modes. The ECS chipset can display a maximum of 16 colours in High Resolution modes (640x256, 640x512, 800x600) and 4 colours in Super High Resolution (1280x256, 1280x512, 1024x768), but it can display 32, 64 or 4,096 colours in Low Resolution (320x256, 320x512) depending on which mode you have it set to. Using a flicker fixer won't reduce any colours, but it will let you use extra modes you couldn't use before!
ECS Amigas have no 256 colour mode, although using the Copper and a few tricks, some games can display more than the standard 32 colours.
Depending on which VGA converter box you go for, you may or may not be able to fill the screen of your monitor without black borders. Some of these boxes have controls to stretch and centre the screen on your monitor, but many don't, so choose wisely and test them first if you can. You won't get as sharp a picture as you would from an Indivision, but it should still give you an image sharp enough to keep you happy, and will definitely be less blurry than Composite.
When using a PCMCIA SRAM card in an A600 you WILL get a speed increase! Contrary to popular belief, these cards are only slow on the 32bit A1200, but not on the 16bit A600! If you run a benchmark program like SysInfo you will see the truth. SRAM on an A600 is fast enough, and increases the overall speed of the computer slightly!
Flashback works provided the PRELOAD option is disabled, and Monkey Island 2 works fine too.