Texas probation (or "community supervision" as it is called in the state) for sex offenders can be wide ranging. These restrictions actually relate to the terms of the probation and not just because someone is required to register as a sex offender. The sex offender statute only relates to an individual's requirement to register with certain agencies. However, for our purposes, this will not be relevant to the discussion.
Restrictions that can be placed on an offender can include, but is not limited to, the following: the prohibition against unsupervised "contact" with minors, polygraph examinations, counseling with qualified professionals, the requirement to obtain court permission before travel and to reside with adults only during the travel, submission to "field testing" by the probation officer (random searches of your employment and residence), random drug testing, GPS monitoring (if required by the court). These are some of the usual requirements of probation. Some are more always applicable, while others are usually rare and depend on the type and nature of case for which probation was received.
There is also a "child safety zone" which is usually only applied in sex offenses involving a child. This safety zone prohibits sex offenders from supervising or participating in any program that includes as participants or recipients persons 17 years of age or younger and that regularly provides athletic, civic activities or going on or withing a specified distance of a premises where children commonly gather (like schools or playgrounds). There may also be a requirement that must live at least 1,000 feet away from these locations as well.
As for limitations that would inhibit building a family, that is something you would have to be concerned with if the person's victim was a minor or child.
These limitations I discussed, again, are not applied in every situation. When you mentioned "low risk" I assume that this person we are discussing did not commit an offense against a minor, so many of these requirements would usually not be placed on the individual.
If you have any follow up questions, please let me know. Otherwise, please leave a positive feedback reviewing my answer.
***It is always best to consult with an attorney who practices in your jurisdiction. They will be more familiar with the laws and procedures applicable in this question.***