General guidance of a few issues i found while researching ncp (drive isolation)

Hi and welcome to my first post

i am currently a user of an Openmediavault nas shared over smb/cifs on my local network
which consists of a linux laptop, a windows desktop and said nas currently hosted on an rpi2

i came across the nextcloudpi over a suggestion on the raspberry pi forums over a particularily nas related topic

i have since scoured the internet for information on ncp and similar setups but came to the conclusion ncp would seem like the optimal choice i however after reading most of the introductionary stuff came across pointers to a setup i would like to do but since port forwarding is necessary for ncp i came across a couple of woes

particulary taking those notes from these 2 posts i read
(https://ownyourbits.com/2017/04/18/different-ways-to-access-your-nextcloud-files/) this post explaining the access to said files but not telling me entirely how limiting i can be
and this post
(How do I mount a NextCloud server drive using SFTP, as a virtual drive on Windows?) telling me how limiting i can be

my setup for the ncp would be to put it on the current rpi i have omv on, to have 2 drives
drive no 1 would only be a smb/cifs file drive to have to share between my local network ONLY and drive 2 would host all ncp files along with a sync to drop files to over the nextcloud app on android, and or other supported platforms.
Is ncp configurable so that my drive no 1 would not broadcast to the internet at all to avoid ransomware attacks and other malicious intent possibly coming from the internet, i ask this because i know i have to open up ports to configure out nextcloud for said project
This being said i apologize for any miss-communication stemming form this post as english is not my native language, and request that in the case that this post is miss-categorized, that this post be properly categorized by moderation.

i would appreciate any guides in the matter as i have so far only seen general setup guides,

with regards,