For this year's winter Sth Pacific islands cruise I left NZ with:
Standalone chart plotter with recent C Map card (Sept 18)
Laptop running Open CPN loaded with all LINZ charts and last version of CM93
Tablet, initially only loaded with Fiji mariners guide app (compilation of google map photos for Fiji).
Open CPN was ok in Tonga as it is running LINZ charts albeit with some gaps, eg no raster charts for the Ha'apais.
Then downloaded Navionics and this has become principal reference charts for coastal navigation around Fiji and now Vanuatu.
The charts available for Open CPN just do not have sufficient detail and neither did the C Map card in the chart plotter, eg the C Map card had no soundings for the Western Yasawas. I queried C Map on this and they advised they have only just incorporated these soundings (and others) in their June 2019 release.
I have since picked up a comprehensive set of google earth photos for the sth pacific which has been installed to run with Open CPN.
Whilst in Western Fiji where I had good internet access(have a cell phone booster aerial running to a mifi modem) I was running google map live, it was very good for picking up reef outlines.
I am finding I use the Chart plotter for ocean passages (and an ocean chart open on the chart table) and the tablet on the coast. I really only look at OpenCPN for the google photos, whereas back on NZ coast it is my preferred reference