I use these three apps on my iPad Pro 12.9”:
Seaiq USA (this will give you NOAA raster charts that are paper charts displayed digitally and USACOE vector charts updated weekly)
Navionics USA & Canada (proprietary cartography updated constantly)
Aqua Maps USA (proprietary cartography updated constantly)
All three of the above apps can display current “crowd sourced” data about anchorages, marinas, and navigation hazards. Seaiq can display only data from Waterway Guide, Navionics displays only Active Captain (both are owned by Garmin), and Aqua Maps can display both.
I use these at the helm of my 2012 Ranger Tug R27 that is equipped with a Garmin 5212 chartplotter. The charts on the 5212 are dated, but I use it mostly to display radar, sonar, GPS course, time, distance, and fuel used.
As has been related above, the iPad display will wash out in direct sunlight and overheat if left in it long enough. The helm of my Ranger Tug is inside so that’s not a problem. I have used the iPad Pro at the helm of an open bow boat and it’s usable most of the times of the day. If it’s mid-day, I shade the helm with a bimini.
On both boats, I use a RAM mount to hold the iPad. The RAM mount is secured by suction cups to window glass. I use a Lightning charging cable plugged into a 12 volt outlet for power, otherwise battery life will be a 2-3 hours.
I use a Dual GPS 160 Bluetooth GPS for position data.
I also use ForeFlight on the iPad.