You can use several plugins for one channel without using a chainer.
Here's a small tutorial to do so:
Go to the general tab
On the bottom of the screen with effects, select FX slot 1. Put an effect in it.
Select FX slot 2. Put another effect in slot 2.
Select slot 1 again. On the right, you see output. Set this to FX2.
If you've done it right, you've created a chain of 2 effects. You can then assign FX slot 1 to a channel or instrument and it will set the chain to that channel/instrument.
Do note: you can only route to an FX slot that has a higher number than the current slot. So if you are on FX 6, you can only route to 7 and higher, but not 5 and lower. Also, in order to see that slot in the list, a plugin must be loaded first.
It doesn't matter if the plugin is an effect or instrument, but only the first item in the chain will get midi information send to, so putting an instrument in a later slot than the 1st of your chain (doesn't have to be fx1) will most likelly not work.
Example of an instrument chain:
FX10 - Crystal VSTi > output to FX11
FX11 - Parametric EQ > output to FX12
FX12 - Compressor > output to FX13
FX13 - Reverb > (default setting: output to master)
Output to FX10, Midi ch 1, samples: none.
To answer your second question:
It is possible in MPT 1.16, but its highly recommended to switch to atleast 1.17 RC2 as the VST(i) support is so much better in these versions.
in 1.16 you'll have to do it manually.