you might be interested to try liveiso xubuntu-bionic nvidia-390.48

a live_iso bionic-xubuntu with nvidia-390.48 prime-switchabled to experiment :
it's working on Acer VN7 4GB ram

boot the live iso http://sourceforge.net/projects/toysbox/ xubuntu-18.04-4.15.0-24-nvidia390.48.iso
open a terminal ctrl-T : inxi -G to check on which graphic card it is running
sudo prime-select query gives equivalent result on running graphic card
sudo prime-select intel to switch to the intel graphic
sudo prime-select nvidia to switch to the nvidia graphic

The prime version here is from Mathieu Gras ( problem and partial solution originally raised up by Tim Richardson )

https://devtalk.nvidia.com/default/topic/1032482/linux/optimus-on-ubuntu-18-04-is-a-step-backwards-but-i-found-the-first-good-solution/4

but to make the whole stuff running as liveIso requires lots of sweats ...and funs !!!!!

Here is a short log :

$ cat Live-xubuntu-bionic-nvidia-390.log

xubuntu@xubuntu:~$ cat /proc/cmdline
BOOT_IMAGE=(loop)/casper/vmlinuz iso-scan/filename=/iso/xubuntu-18.04-4.15.0-24-nvidia0.iso file=/cdrom/preseed/xubuntu.seed waitusb=5 boot=casper systemd.debug-shell=1 systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M printk.devkmsg=on

xubuntu@xubuntu:~$ uname -a
Linux xubuntu 4.15.0-24-generic #26-Ubuntu SMP Wed Jun 13 08:44:47 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

xubuntu@xubuntu:~$ inxi -G Graphics:
Card-1: Intel 4th Gen Core Processor Integrated Graphics Controller
Card-2: NVIDIA GM107M [GeForce GTX 860M]
Display Server: x11 (X.Org 1.19.6 ) drivers: modesetting,nvidia (unloaded: fbdev,vesa,nouveau) Resolution: 1920x1080@60.02hz OpenGL: renderer: GeForce GTX 860M/PCIe/SSE2 version: 4.6.0 NVIDIA 390.48

xubuntu@xubuntu:~$ xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x23a cap: 0x1, Source Output crtcs: 0 outputs: 0 associated providers: 1 name:NVIDIA-0 Provider 1: id: 0x44 cap: 0x6, Sink Output, Source Offload crtcs: 3 outputs: 2 associated providers: 1 name:modesetting

xubuntu@xubuntu:~$ glxinfo | grep NVIDIA
server glx vendor string: NVIDIA Corporation client glx vendor string: NVIDIA Corporation
OpenGL vendor string: NVIDIA Corporation
OpenGL core profile version string: 4.6.0 NVIDIA 390.48
OpenGL core profile shading language version string: 4.60 NVIDIA
OpenGL version string: 4.6.0 NVIDIA 390.48
OpenGL shading language version string: 4.60 NVIDIA
OpenGL ES profile version string:
OpenGL ES 3.2 NVIDIA 390.48

xubuntu@xubuntu:~$ glxgears
Running synchronized to the vertical refresh. The framerate should be approximately the same as the monitor refresh rate.
69297 frames in 5.0 seconds = 13859.334 FPS
68090 frames in 5.0 seconds = 13617.823 FPS

xubuntu@xubuntu:~$ glxspheres64
Polygons in scene: 62464 (61 spheres * 1024 polys/spheres) Visual ID of window: 0xa8 Context is Direct OpenGL Renderer: GeForce GTX 860M/PCIe/SSE2
1914.953887 frames/sec - 2137.088538 Mpixels/sec
1964.035952 frames/sec - 2191.864122 Mpixels/sec

Troublshootings

1 If at boot you get a black screen ...really nothing else after 2min don't panic ;
Open a VT2 with ctrl-F2 Login as xubuntu user with blank password ;
sudo su to get root permission
lsmod | grep nvidia_drm check if module nvidia-drm.ko is loaded , in which case simply
Type systemctl stop lightdm then systemctl start lightdm
or simply
systemctl restart lightdm

If no module nvidia loaded then try switch on nvidia card by ( check presence of module bbswitch with cat /proc/acpi/bbswitch )
echo "ON" >/proc/acpi/bbswitch
it will switched to good nvidia'card desktop or ...blackscreen ,then restart ligthtdm

2 The desktop boots but inxi -G shows no graphic on nvidia but only intel-graphic with intel_driver or modesetting_driver .
If lsmod | grep video shows lots of nvidia modules ;
it means then Xorg server auto detection scheme misses setting up GPU correctly a.k.a nvidia'graphic card as source output and intel's iGPU as sink output as defined by Optimus technology.
Simply sudo systemctl restart lightdm from desktop's terminal and we get the right desktop with drivers: modesetting,nvidia (unloaded: fbdev,vesa,nouveau) shown by inxi -G. 3

There are very few commands to know helping solving ,understanding the troubles
lsmod | grep nvidia to make sure that nvidia-drm.ko is loaded before starting again lightdm
echo "ON">/proc/acpi/bbswitch to switch on the nvidia graphic card
systemctl to start systemd service

4 Of course if it happens you see "nouveau" module present on lsmod then you really need to stop lightdm before removing rmmod nouveau otherwise nvidia would conflict

5 I setup a rc-local.service to be able to give xubuntu user sudo without passwd ,and switch on nvidia card during boot time