Do you think it's unfair even if the AI has the same start?
Yes.
There's something you have to understand about the AI in this game: it's pretty stupid. It doesn't PLAN, that much is obvious, but there are also a lot of hard-coded behaviors, and changing certain things will cause the AI to behave... poorly. It can still make for an enjoyable game, but that still doesn't make it anywhere close to a challenge for a skilled player unless you give massive handicaps.
For instance, take your road change. In the normal game, the roads and railroads cost money, so you will only make just enough to connect your cities. If you drop the maintenance costs to zero, the best strategy will be "Pave the Earth", like in older Civ games where every tile would have a railroad. Sure, the extra roads might be lower in priority, but for military reasons it's still a good thing to do when you have time.
But the AI won't know to do this. It'll continue to follow the current behavior, where it just builds enough roads to keep cities connected.
Likewise, railroads take time to build, twice as long as a normal road. You, as a player, know when to hold off on actions that take too long, when you've got something else to be built, but eventually you'll hit the point where building that railroad is more desirable than adding yet another non-resource Farm and you've got enough workers to spare that locking one into a long-duration action won't cripple you. The AI doesn't prioritize like that; if option A is more desirable than option B right now, then it'll STAY more desirable forever (barring a couple hard-coded AI behaviors, like "need more workers" or "need more Happiness").
Or the free Workers. Sounds straightforward, but two workers for a city that only has six workable hexes means that unless you get new Settlers out ASAP (either building them or taking the Liberty policy that gives you one), you'll be left with Workers that have nothing to do. A human will have them scout, or start building roads towards the eventual expansion sites. But the AI will just park one in its city and wait for a border expansion, and the other will probably get captured by a Barbarian.
The point is, most mods invariably make life harder for the AI, because they add new systems that a player can easily adjust to but the AI will continue to play the same way it always did. However, note the "most"; many balance mods (my own included) attempt to fix the game by making the strategies the AI already practices fall closer to the optimum. ICS was a good example of this; everyone saw how unbalanced a strategy it was to pack as many small cities into an area as possible and then load up on Scientist specialists. So, many balance mods tried different ways to discourage that strategy; the AI wouldn't be affected, because it wasn't doing that to begin with, but it'd now force the player to play in a way more similar to that used by the AIs.
