On the former it would depend for me on how deep they tended to drop. I think your Albert example possibly falls into that category. On Ronaldo and Vieri, Ronaldo generally played deeper than Vieri and improved his passing when playing there. Ronaldo played off Vieri as it were
Well one of them probably always would be slightly ahead of the other, but I don't necessarily think that is enough to be classified as a second striker.
Was just googling for its definition on the internet and Wikipedia puts my thoughts very well
Second striker
Deep-lying forwards have a long history in the game, but the terminology to describe their playing activity has varied over the years. Originally such players were termed inside forwards, creative or deep-lying centre-forwards ("sub forwards"). More recently, two more variations of this old type of player have developed: the second, or shadow, or support, or auxiliary striker and, in what is in fact a distinct position unto its own, the number 10;
[10][11] the former role is exemplified by players such as
Dennis Bergkamp (who would play just in behind the striker
Thierry Henry at
Arsenal),
[12] Alessandro Del Piero at
Juventus,
[13] Youri Djorkaeff at
Inter Milan,
[14][15][16] or
Teddy Sheringham at Manchester United.
[17] Other creative players who play further back, such as
Diego Maradona,
Ronaldinho and
Zinedine Zidane, are often instead described as the "number 10," and usually operate as an
attacking midfielder or advanced
playmaker.
[18]
The second striker position is a loosely defined and most often misapplied description of a player positioned in a free role, somewhere between the out-and-out striker, whether he or she is a "target-man" or more of a "poacher", and the number 10 or attacking midfielder, while possibly showing some of the characteristics of both. In fact, a term coined by French advanced playmaker
Michel Platini, the "nine-and-a-half", which he used to describe the playing role of his successor in the number 10 role at Juventus, Italian playmaker
Roberto Baggio, has been an attempt to become a standard in defining the position.
[19] Conceivably, a number 10 can alternate as a second-striker provided that he or she is also a prolific goalscorer; otherwise, a mobile forward with good technical ability (
dribbling skills and ball control), acceleration, vision, passing, and link-up play, who can both score and
create opportunities for a less versatile centre-forward, is more suited. Although they are often given "licence to roam," and either run forward, or drop further back in order to pick up the ball in deeper areas, giving them more time and space in possession, second or support strikers do not tend to get as involved in the orchestration of attacks as the number 10, nor do they bring as many other players into play, since they do not share the burden of responsibility, functioning predominantly in a supporting role as
assist providers.
[20][21] In Italy, this role is known as a "rifinitore" or "seconda punta",
[22] whereas in Brazil, it is known as "segundo atacante"
[23] or "ponta-de-lança".
[24]