Basic Win and Linux VM initial config/setup guidance : resize / data share

first post. i have experience with vbox and some vmware prior to coming here but i am totally unfamiliar with parallels. i just ordered a mbp and want to configure 2 vm guests under parallels when the laptop arrives. with vbox and vmware, once you some configuration decisiions and install into the vm guest, you're often stuck with what you have or have to jump through hoops if you change you mind later. so i'm trying to get some guidance from people who've already used parallels BEFORE i actually do my installs to hopefully prevent any later pain.

more specifically i'm going to :

1) installing win 8.1 pro in a seperate vm guest
2) install linux in a vm guest

my goals are to :

a) install the base OS in both vms using an appropriate amount of HD space. by appropriate, i mean i 'd prefer to allocate just the right amount to accomodate what i'm currently going to actually use and have the size be EASILY adjustable later if i need more space. by easy i mean either on the fly or easy to just add to it. increasing disk space in other virtual managers isn't often easy or without risk. it often involves reformatting etc which means you risk data loss if you don't specify the exact parameters correctly (linux) and i've never tried to do it in windows.

what's the best way to configure the original guest installs in parallels to get what i want? is on the fly resizing of a virtual disk / partition supported in parallels and if so is it easy / transparent and does it drastically reduce performance in some way. what's the parallel lingo fro doing what i want to do if it uses it's own terminology.

b) find the best way to share (aka EASILY access and backup HOPEFULL ONE SINGLE set of SHARED data between all of the mac host, windows guest and linux guest. i know i can drag and drop files from host to guest (and i imagine guest to guest too?) easily using parallels. But that creates copies all over the place. the ideal situation would be to create and keep all the shared data in one place and then have that location be EASILY accessible from all three locations. i don't care if the one place natively lives on the mac host, or either of the win or linux guests. i just want one want location with easy maintainence / access from all three.

so what's the best way to approach this in parallels per my requirements above including any parallel jargon to achieve this in specific concrete terms? i know that linux can mount ntfs file systems but i don't think the vice versa is true. i believe that osx can mount ntfs as well. so perhaps the best thing would be to create an additional win virtual ntfs DATA disk along with a the separate win vm OS disk? similar to the above OS question, my hope is that the ntfs data disk could be resized automatically on the fly or easily by some other parallels utility when / if more size was needed? the question is then do i have to mount this ntfs data vdisk in both the mac host andr linux guest or does parallels provide some magic to make the sharing happen easier than that? perhaps i'm barking up the wrong tree and there is a better solution?

sorry for the long post but trying to be clear. anybody that has installed and run vms should understand my concerns as they're quite common and getting the initial config right goes a long way to saving pain later. hopefully some people out there can point me in the right direction directly with replies or referencing useful links basedon actual experience and useful recommendations.

thanks