Welcome to Gaia! ::

Two things come to me at the moment.

One:
I am willing to bet more than 80% of what you read on 'Wicca' had nothing to do with Wicca proper. Misinformation is everywhere, and unfortunately includes the majority of published, publicly-available materials. Wicca is a hard polytheistic religion - meaning it does believe that there are many different gods and pantheon, and that their own Gods are distinct and individual. It just happens that the Wiccan pantheon is a pantheon of two, its' Lord and Lady.

Wicca doesn't give a flying fig that someone believes in and works with other deities or pantheons. They just can't do it within the Wiccan religion. Wicca's rites and practices are for the Lord and Lady alone. Altering the rites to fit outside influences renders them 'not-Wicca'. They become something else.

Wicca is also orthopraxic. That is, what matters is what you do and how you do it - meaning that you perform the rites properly, and know the proper methods for preparing and working the different aspects of the religion. Wicca doesn't have beliefs. Individual Wiccans can believe, comprehend, and explain the workings of their universe and what's in it however they like - what makes them Wiccan is having passed through initiation the same as all other Wiccans, and to be trained in the proper methods of Wiccan practice. Inside the same coven, you may (and will) find that individuals have very different beliefs from one another but can work together effectively because they all share the same religious framework.

Two:
There's no 'Celtic' paganism. 'Celtic' is a linguistic term, used to denote a family of languages. Outside that usage, it's practically meaningless. There are peoples who speak Celtic languages,
but those nations are spread across Europe and their pantheon and practices are very different from one another. Some overlap Germanic or Slavic cultures, as well, and there are historically degrees of blending in places. There isn't a universal, over-arching pantheon or religion that represents all the Celts.

Generally speaking, people tend to look to the 6 Celtic Nations of the British Isles - Ireland, Scotland, Wales, Brittany, the Manx, and Cornwall. But there were also pockets of Celtic-speaking peoples in Galicia (now Spain), as well as the Gaulish peoples who spread across huge portions of Europe.
Some of these religions were blended with Germanic religion. Others were invaded by the Romans and blended in with those names and practices.

A few notes:
Scotland was settled by the Irish, and had a native population of Picts. We know little of those original inhabitants, and their religion. Scotland has ended up a blend of things, from Ireland, the Picts, and the Norse, through many invasions. Most of the modern associations we have with Scotland are in fact from the 18th century, when the English cleared out huge numbers of the Scottish populations from the highlands, and created a sort of twee, socially-acceptable version of Scottish heritage.

Information about the Breton people, and the Galicians is scarce.

The Gauls break down in to hundreds of different peoples, each with their own specific gods that may not be worked with outside a specific locality. Many were blended with the Roman gods, and farther north Germanic peoples overlapped their lands. There's not a huge amount of information there, unless you're a real scholar and willing to dig.

1) In parallel, yes. You can't cross the streams.

I feel you may have missed the point I was making, though. Wicca is practice-based, not belief-based. There are no beliefs that can make one Wiccan, and you can't just give yourself membership amongst the Wica because you believe you're Wiccan. Wicca is initiatory, and initiation is earned through hard work and proper personhood. You are brought into the Wica by others.

If you want to pursue Wicca, by all means do. But understand that if you're learning it from a book, on your own, it isn't Wicca. At best, it's eclectic neo-paganism that tries really hard to imitate what it's seen (or thinks it's seen) of Wicca. (ENP is perfectly valid as a path on its' own, but just shouldn't be called Wicca.) You'll need a proper coven to learn from, and eventually be initiated into, to be an actual Wiccan. Until such a time, you would be called a Seeker - a Seeker of Wicca - and you can feel free to practice whatever other religion or spirituality works for you, and doesn't conflict with the requirements of either Wicca, or the other.

2) That's some interesting synesthesia. I also experience the blending of senses with words and other concepts. However, around these parts it helps to be specific as possible. You can also use the word 'Gaelic' - I often identify as a 'Gaelic polytheist', and this specifically refers to the Irish as well.