If you are able to take the train from La Coruna to Ferrol instead of the bus (depends, of course, on whether the train times are efficient for your arrival), the train will go right round the estuary where the Camino Ingles goes. You will then see what you will miss if you walk across the N-651 bridge from Ferrol to Fene and then on to Pontedeume from then. You will also see what the N-651 bridge cuts out. Taking the train may help you make up your mind.
Also, you need to remember that the N-651 bridge comes up a good hour into the first stage, so you can decide how you feel at that point, what the time is, weather, etc., depending on how you are going.
One other 'trick'. If you have time on your arrival into Ferrol and can walk the 2 km from the start of the Ingles at the harbour until the Ingles leaves the old town, this knocks 2km or 30 minutes off the walk the next day, as you have done it the night before. All you need on the first day is a stamp from Ferrol, and hopefully, you should be able to obtain this from the hotel you stay in.
If you only have 5 days, if you don't take the short cut over the N-651 bridge, you either need to walk the 29km all the way round the estuary from Ferrol on day 1, or stay at either Neda or Xubia on day 1, and then on day 5, walking 40km on the last day from somewhere around Bruma to Santiago. Taking the N-651 bridge knocks about 8km off the first stage, but at, still, over 20km, is still a long walk for some on the first day.
In terms of difficulty on the Ingles, now that the big climb up to Hospital de Bruma has been replaced by an easier, gradual climb, the only difficulty on the Ingles on a 5 day walk is the long stages (20 - 25km plus each, and every, day). There are two 20 - 30 minute climbs out of Pontedeume and Betanzos, on tarmacked roads, but these are at the very start of a day, when hopefully you will be fresher. Another thing to note is that facilities (bars, shops, restaurants, water fountains) don't appear every 3 km or so, and you may well find that these are some 10km apart in some parts. This can catch some people out who are unprepared. The final thing to note is that about half the Ingles is on asphalt, but in the main, you are walking on country roads.
Don't let any of this put you off the Ingles. It is a great walk, especially on the first two days when you walk round the coast, and for those who only have a week, far better, in my opinion, than jumping on the Frances at Sarria. It is a different feeling when you arrive in Santiago having walked a whole Camino. The Ingles is also much quieter, and gives you a genuine pilgrims experience.