I'm no specialist of the question but I'm alsatian and from a quick search and common knowledge around here I can try and give you the beginning of an answer:

First, speaking of Alsace-Lorraine per say is not really accurate, the territory that was annexed to the german Empire in 1871 is comprised of Alsace and part of the Lorraine territory that is the Moselle. Both region are in fact quite different and Alsace and alsatian are still very touchy about this and their peculiarity (there is currently a very strong identitary movement here as Alsace is gonna be paired with Lorraine and Champagne Ardennes to make a big east region part of the new French region map but that is another subject :) ). As for how german was Alsace at the time, the answer is complex :

• after being a free region for a long time, neither French nor completely German thanks to Strasbourg and Mulhouse's "free city" status, the region was annexed by France at the end of the the 17th century and it's only towards the end of the 19th century that the french efforts to integrate the region to France started to have an effect of making Alsatian feel French. There was also a big impact from the french revolution since the Alsatian bourgeoisie was a big support to the revolutionnaries, eager to get rid of the monarchy and gain more independance in the process, this pushed towards making Alsatian feel French too, along with the urban improvements that were made after the revolution by France. What was more of an issue was the religious beliefs from the population : catholics were happy to be French, but protestants were always torn between France and Germany. This meant that when Alsace got back to the german Empire, catholics were extremely unhappy unlike protestants. As a result protesting groups formed at the time and 128 000 alsatian were allowed to leave Alsace and go back to France. Despite being considered a semi-autonomous Land (a bit like today's german Länder) from 1911 Alsace remained rather opposed to the German ruling and the tensions piked with the "Affaire de Saverne"or Saverne gate where a german officer humiliated Alsatian populations which ultimately led to the first ever non confidence motion being voted against the German Imperial Chancellor at the Reichstag.

However, Germany did rebuilt Alsace after the 1870s bombings and did it quite thoroughly in Strasbourg where I live and where impressive german Imperial buildings still stand next to centuries old traditionnal houses (particularly around the square of the Republic, wittingly renamed but originally built around Wilhelm Ist's palace). We also acquired the bismarckian social protection system which is very advantageous and was kept after 1945 (still applying today as an exception to the general French system in Alsace-Moselle).

If you're ever around Strasbourg, i advise you to go to the historical museum which is all new and very well displayed, you shall find information there which will surely help you with your inquiries :)

Source : french wikipedia & http://www.jds.fr/tourisme-et-loisirs/guide-de-l-alsace/l-alsace-allemande-de-1870-a-1918-34630_A

From what I can read in “L’Alsace des notables 1870-1914 — La bourgeoisie et le peuple alsacien” (François Igersheim, 1981) both the Alsatian bourgeoisie and worker class would consider themselves to belong to Germany before the Great War.

Translated excerpts from the book's conclusion.

p182:

The German socialist Wendel, born in Metz, says [in 1918]: “If, before the War, there was a referendum on whether Alsace should belong to Germany or France, four fifth of the inhabitants would vote, by realism [implying not necessarily by heart], for Germany. However, today, an overwhelming majority supports France, not out of love for the Tricolour, but out of bitterness and hatred due to what has been done to Alsace-Lorraine from the 31 of July 1914 on.”

p183:

While the Versailles government killed on behalf of the whole European bourgeoisie the Paris Commune, and shot the Communards, the Alsacian bourgeoisie, relieved to be under the strong protection of its new overlords, reaches agreements with them, in economic and social matters, while maintaining the French law, now local law.

p185:

[For Alsatian marxists], Alsace has an historical duty to transform Germany into a Republic, and contribute to the France-Germany peace.