Are 19th century testaments different from those of preceding centuries?

Yes, the 19th century saw changes in the format and character of testaments. Until 1824 testaments were confirmed by commissary courts, but after that date they became the responsibility of the sheriff courts. So inevitably there were some changes. But even before 1824 you may notice some differences. These came about as a result of clauses in the Revenue Acts of 1804 and 1808. Briefly, separate registers of inventories, confirmations and settlements (wills) were kept, and it was possible for an executor to register an inventory with the court without seeking confirmation. And, of course, you should find 19th century testaments much easier to read.

If I know the date of death for someone, should I restrict the search for his or her testament to a few years on either side of the date of death?

No, it is worth checking the indexes well beyond the date-range you are considering searching. Occasionally, the intervention of the court to settle the deceased’s affairs was not required until many years after the death, possibly as a result of a dispute.

Is there any point in searching for the testament of an Englishman or Englishwoman in Scottish records?

Probably not, unless you think there is a chance that he or she might have held some assets in Scotland, in which case you should definitely undertake this search. The registers of the principal commissary court in Edinburgh will be the ones to try. This court had responsibility in testamentary matters not only for Scots who died ‘furth of the realm’ but also for English people who may never have resided in Scotland but who held Scottish assets, even if it was only money in a Scottish bank account.