I am one turn away from completing Magellan's Voyage and one of JS Bach's Cathedral or Smith's Trading Company.
What map size/type? What intended VC?
Both GWs have global effects, so it basically comes down to which you think would save you more money? Reducing the LUX%-slider, or paying for all the Harbours, Markets, (Banks, StockExes,) CommDocks, and Airports that you have (or may want to build later)?
Or a more radical option: why not take both Bachs
and Smiths, and let the AI have Magellans? MagVoy only adds M+1 to your ships, which I've never found to be very useful in the epic-game (especially on smaller maps and/or those with 60% water, where channels are usually narrow(er) enough that +1 move won't usually shorten the turns needed to make the crossing).
I currently have a mutual protection pack with England, and they have one with the Celts. What happens if I start a war with the Celts? Does England have to choose which side to support, or does nothing happen? Thanks!
MPPs are triggered when one of the MPP-partners is attacked within their own borders (including cross-border kidnapping of unprotected Workers, bombardments, or Zone-of-Control strikes on any passing MPP-protected unit).
I
believe an MPP will also be triggered if a declared enemy simply ends their turn with units inside one of the MPP-partners' borders, even without any attacks yet having been made.
Literally the next turn the Celts declared war on me, and England declared war on them. Maybe if a civ is allied with two other civs in a war, whichever of those declared war first loses the support with the allied civ?
If Brennus declared on you by sneak-attacking, then yes, that would have triggered your MPP with the English, causing Liz to declare on Brennus in response.
But even if Brennus hadn't co-operated with your plan to go to war with him, then provided your border-towns were garrisoned sufficiently to prevent their loss (or even to encourage his units to bypass them in favour of softer targets further inside your borders), you could also have 'safely' declared on him, and let the Celtic units attack you over the interturn, to accomplish the same result.